EMBRYOPSIDA Pirani & Prado
Gametophyte dominant, independent, multicellular, not motile, initially ±globular; showing gravitropism; acquisition of phenylalanine lysase [PAL], microbial terpene synthase-like genes +, triterpenoids produced by CYP716 enzymes, phenylpropanoid metabolism [lignans +, flavonoids + (absorbtion of UV radiation)], xyloglucans in primary cell wall, side chains charged; plant poikilohydrous [protoplasm dessication tolerant], ectohydrous [free water outside plant physiologically important]; thalloid, leafy, with single-celled apical meristem, tissues little differentiated, rhizoids +, unicellular; chloroplasts several per cell, pyrenoids 0; glycolate metabolism in leaf peroxisomes [glyoxysomes]; centrioles/centrosomes in vegetative cells 0, microtubules with γ-tubulin along their lengths [?here], interphase microtubules form hoop-like system; metaphase spindle anastral, predictive preprophase band + [with microtubules and F-actin; where new cell wall will form], phragmoplast + [cell wall deposition centrifugal, from around the anaphase spindle], plasmodesmata +; antheridia and archegonia jacketed, surficial; blepharoplast +, centrioles develop de novo, bicentriole pair coaxial, separate at midpoint, centrioles rotate, associated with basal bodies of cilia, multilayered structure + [4 layers: L1, L4, tubules; L2, L3, short vertical lamellae] (0), spline + [tubules from L1 encircling spermatid], basal body 200-250 nm long, associated with amorphous electron-dense material, microtubules in basal end lacking symmetry, stellate array of filaments in transition zone extended, axonemal cap 0 [microtubules disorganized at apex of cilium]; male gametes [spermatozoids] with a left-handed coil, cilia 2, lateral; oogamy; sporophyte multicellular, cuticle +, plane of first cell division transverse [with respect to long axis of archegonium/embryo sac], sporangium and upper part of seta developing from epibasal cell [towards the archegonial neck, exoscopic], with at least transient apical cell [?level], initially surrounded by and dependent on gametophyte, placental transfer cells +, in both sporophyte and gametophyte, wall ingrowths develop early; suspensor/foot +, cells at foot tip somewhat haustorial; sporangium +, single, terminal, dehiscence longitudinal; meiosis sporic, monoplastidic, MTOC [MTOC = microtubule organizing centre] associated with plastid, sporocytes 4-lobed, cytokinesis simultaneous, preceding nuclear division, quadripolar microtubule system +; wall development both centripetal and centrifugal, 1000 spores/sporangium, sporopollenin in the spore wall laid down in association with trilamellar layers [white-line centred lamellae; tripartite lamellae]; nuclear genome size [1C] <1.4 pg, main telomere sequence motif TTTAGGG, LEAFY and KNOX1 and KNOX2 genes present, ethylene involved in cell elongation; chloroplast genome with close association between trnLUAA and trnFGAA genes [precursors for starch synthesis], tufA gene moved to nucleus; mitochondrial trnS(gcu) and trnN(guu) genes +.
Many of the bolded characters in the characterization above are apomorphies of subsets of streptophytes along the lineage leading to the embryophytes, not apomorphies of crown-group embryophytes per se.
All groups below are crown groups, nearly all are extant. Characters mentioned are those of the immediate common ancestor of the group,  contains explanatory material, () features common in clade, exact status unclear.
Abscisic acid, L- and D-methionine distinguished metabolically; pro- and metaphase spindles acentric; sporophyte with polar transport of auxins, class 1 KNOX genes expressed in sporangium alone; sporangium wall 4≤ cells across [≡ eusporangium], tapetum +, secreting sporopollenin, which obscures outer white-line centred lamellae, columella +, developing from endothecial cells; stomata +, on sporangium, anomocytic, cell lineage that produces them with symmetric divisions [perigenous]; underlying similarities in the development of conducting tissue and of rhizoids/root hairs; spores trilete; shoot meristem patterning gene families expressed; MIKC, MI*K*C* genes, post-transcriptional editing of chloroplast genes; gain of three group II mitochondrial introns, mitochondrial trnS(gcu) and trnN(guu) genes 0.
[Anthocerophyta + Polysporangiophyta]: gametophyte leafless; archegonia embedded/sunken [only neck protruding]; sporophyte long-lived, chlorophyllous; cell walls with xylans.
Sporophyte well developed, branched, branching apical, dichotomous, potentially indeterminate; hydroids +; stomata on stem; sporangia several, terminal; spore walls not multilamellate [?here].
Vascular tissue + [tracheids, walls with bars of secondary thickening]; stomata involved in gas exchange.
EXTANT TRACHEOPHYTA / VASCULAR PLANTS
Sporophyte with photosynthetic red light response, stomata open in response to blue light; plant homoiohydrous [water content of protoplasm relatively stable]; control of leaf hydration passive; plant endohydrous [physiologically important free water inside plant]; (condensed or nonhydrolyzable tannins/proanthocyanidins +); xyloglucans with side chains uncharged [?level], in secondary walls of vascular and mechanical tissue; lignins +; stem apex multicellular, with cytohistochemical zonation, plasmodesmata formation based on cell lineage; vascular development acropetal, tracheids +, in both protoxylem and metaxylem, G- and S-types; sieve cells + [nucleus degenerating]; endodermis +; leaves/sporophylls spirally arranged, blades with mean venation density ca 1.8 mm/mm2 [to 5 mm/mm2], all epidermal cells with chloroplasts; sporangia adaxial, columella 0; tapetum glandular; ?position of transfer cells; MTOCs not associated with plastids, basal body 350-550 nm long, stellate array in transition region initially joining microtubule triplets; suspensor +, shoot apex developing away from micropyle/archegonial neck [from hypobasal cell, endoscopic], root lateral with respect to the longitudinal axis of the embryo [plant homorhizic].[MONILOPHYTA + LIGNOPHYTA]
Sporophyte endomycorrhizal [with Glomeromycota]; growth ± monopodial, branching spiral; roots +, endogenous, positively geotropic, root hairs and root cap +, protoxylem exarch, lateral roots +, endogenous; G-type tracheids +, with scalariform-bordered pits; leaves with apical/marginal growth, venation development basipetal, growth determinate; sporangium dehiscence by a single longitudinal slit; cells polyplastidic, MTOCs diffuse, perinuclear, migratory; blepharoplasts +, paired, with electron-dense material, centrioles on periphery, male gametes multiciliate; chloroplast long single copy ca 30kb inversion [from psbM to ycf2]; mitochondrion with loss of 4 genes, absence of numerous group II introns; LITTLE ZIPPER proteins.
Sporophyte woody; stem branching lateral, meristems axillary; lateral root origin from the pericycle; cork cambium + [producing cork abaxially], vascular cambium bifacial [producing phloem abaxially and xylem adaxially].
Plants heterosporous; megasporangium surrounded by cupule [i.e. = unitegmic ovule, cupule = integument]; pollen lands on ovule; megaspore germination endosporic [female gametophyte initially retained on the plant].
EXTANT SEED PLANTS / SPERMATOPHYTA
Plant evergreen; nicotinic acid metabolised to trigonelline, (cyanogenesis via tyrosine pathway); microbial terpene synthase-like genes 0; primary cell walls rich in xyloglucans and/or glucomannans, 25-30% pectin [Type I walls]; lignin chains started by monolignol dimerization [resinols common], particularly with guaiacyl and p-hydroxyphenyl [G + H] units [sinapyl units uncommon, no Maüle reaction]; root stele diarch to pentarch, xylem and phloem originating on alternating radii, cork cambium deep seated; stem apical meristem complex [with quiescent centre, etc.], plasmodesma density in SAM 1.6-6.2[mean]/μm2 [interface-specific plasmodesmatal network]; eustele +, protoxylem endarch, endodermis 0; wood homoxylous, tracheids and rays alone, tracheid/tracheid pits circular, bordered; mature sieve tube/cell lacking functioning nucleus, sieve tube plastids with starch grains; phloem fibres +; cork cambium superficial; leaf nodes 1:1, a single trace leaving the vascular sympodium; leaf vascular bundles amphicribral; guard cells the only epidermal cells with chloroplasts, stomatal pore with active opening in response to leaf hydration, control by abscisic acid, metabolic regulation of water use efficiency, etc.; axillary buds +, exogenous; prophylls two, lateral; leaves with petiole and lamina, development basipetal, lamina simple; sporangia borne on sporophylls; spores not dormant; microsporophylls aggregated in indeterminate cones/strobili; grains monosulcate, aperture in ana- position [distal], primexine + [involved in exine pattern formation with deposition of sporopollenin from tapetum there], exine and intine homogeneous, exine alveolar/honeycomb; ovules with parietal tissue [= crassinucellate], megaspore tetrad linear, functional megaspore single, chalazal, sporopollenin 0; gametophyte ± wholly dependent on sporophyte, development initially endosporic [apical cell 0, rhizoids 0, etc.]; male gametophyte with tube developing from distal end of grain, male gametes two, developing after pollination, with cell walls; female gametophyte initially syncytial, walls then surrounding individual nuclei; embryo cellular ab initio, suspensor short-minute, embryonic axis straight [shoot and root at opposite ends; plant allorhizic], cotyledons 2; embryo ± dormant; chloroplast ycf2 gene in inverted repeat, trans splicing of five mitochondrial group II introns, rpl6 gene absent; whole nuclear genome duplication [ζ - zeta - duplication], two copies of LEAFY gene, PHY gene duplications [three - [BP [A/N + C/O]] - copies], 5.8S and 5S rDNA in separate clusters.
ANGIOSPERMAE / MAGNOLIOPHYTA
Lignans, O-methyl flavonols, dihydroflavonols, triterpenoid oleanane, apigenin and/or luteolin scattered, [cyanogenesis in ANA grade?], lignin also with syringyl units common [G + S lignin, positive Maüle reaction - syringyl:guaiacyl ratio more than 2-2.5:1], hemicelluloses as xyloglucans; root cap meristem closed (open); pith relatively inconspicuous, lateral roots initiated immediately to the side of [when diarch] or opposite xylem poles; origin of epidermis with no clear pattern [probably from inner layer of root cap], trichoblasts [differentiated root hair-forming cells] 0, hypodermis suberised and with Casparian strip [= exodermis]; shoot apex with tunica-corpus construction, tunica 2-layered; starch grains simple; primary cell wall mostly with pectic polysaccharides, poor in mannans; tracheid:tracheid [end wall] plates with scalariform pitting, wood parenchyma +; sieve tubes enucleate, sieve plate with pores (0.1-)0.5-10< µm across, cytoplasm with P-proteins, not occluding pores of plate, companion cell and sieve tube from same mother cell; ?phloem loading/sugar transport; nodes 1:?; dark reversal Pfr → Pr; protoplasm dessication tolerant [plant poikilohydric]; stomata brachyparacytic [ends of subsidiary cells level with ends of pore], outer stomatal ledges producing vestibule, reduction in stomatal conductance with increasing CO2 concentration; lamina formed from the primordial leaf apex, margins toothed, development of venation acropetal, overall growth ± diffuse, secondary veins pinnate, fine venation hierarchical-reticulate, (1.7-)4.1(-5.7) mm/mm2, vein endings free; flowers perfect, pedicellate, ± haplomorphic, protogynous; parts free, numbers variable, development centripetal; P +, ?insertion, members each with a single trace, outer members not sharply differentiated from the others, not enclosing the floral bud; A many, filament not sharply distinguished from anther, stout, broad, with a single trace, anther introrse, tetrasporangiate, sporangia in two groups of two [dithecal], each theca dehiscing longitudinally by a common slit, ± embedded in the filament, walls with at least outer secondary parietal cells dividing, endothecium +, cells elongated at right angles to long axis of anther; tapetal cells binucleate; microspore mother cells in a block, microsporogenesis successive, walls developing by centripetal furrowing; pollen subspherical, tectum continuous or microperforate, ektexine columellate, endexine lamellate only in the apertural regions, thin, compact, intine in apertural areas thick, pollenkitt +; nectary 0; carpels present, superior, free, several, ascidiate [postgenital occlusion by secretion], stylulus at most short [shorter than ovary], hollow, cavity not lined by distinct epidermal layer, stigma ± decurrent, carinal, dry; suprastylar extragynoecial compitum +; ovules few [?1]/carpel, marginal, anatropous, bitegmic, micropyle endostomal, outer integument 2-3 cells across, often largely subdermal in origin, inner integument 2-3 cells across, often dermal in origin, parietal tissue 1-3 cells across, nucellar cap?; megasporocyte single, hypodermal, functional megaspore lacking cuticle; female gametophyte lacking chlorophyll, not photosynthesising, four-celled [one module, nucleus of egg cell sister to one of the polar nuclei]; ovule not increasing in size between pollination and fertilization; pollen grains land on stigma, bicellular at dispersal, mature male gametophyte tricellular, germinating in less than 3 hours, pollen tube elongated, unbranched, growing towards the ovule, between cells, growth rate (20-)80-20,000 µm/hour, apex of pectins, wall with callose, lumen with callose plugs, penetration of ovules via micropyle [porogamous], whole process takes ca 18 hours, distance to first ovule 1.1-2.1 mm; male gametes lacking cell walls, ciliae 0, siphonogamy; double fertilization +, ovules aborting unless fertilized; P deciduous in fruit; mature seed much larger than fertilized ovule, small [<5 mm long], dry [no sarcotesta], exotestal; endosperm +, cellular, development heteropolar [first division oblique, micropylar end initially with a single large cell, divisions uniseriate, chalazal cell smaller, divisions in several planes], copious, oily and/or proteinaceous, embryo short [<¼ length of seed]; plastid and mitochondrial transmission maternal; Arabidopsis-type telomeres [(TTTAGGG)n]; nuclear genome size [1C] <1.4 pg [mean 1C = 18.1 pg, 1 pg = 109 base pairs], whole nuclear genome duplication [ε/epsilon event]; ndhB gene 21 codons enlarged at the 5' end, single copy of LEAFY and RPB2 gene, knox genes extensively duplicated [A1-A4], AP1/FUL gene, palaeo AP3 and PI genes [paralogous B-class genes] +, with "DEAER" motif, SEP3/LOFSEP and three copies of the PHY gene, [PHYB [PHYA + PHYC]]; chloroplast chlB, -L, -N, trnP-GGG genes 0.
[NYMPHAEALES [AUSTROBAILEYALES [[CHLORANTHALES + MAGNOLIIDS] [MONOCOTS [CERATOPHYLLALES + EUDICOTS]]]]]: wood fibres +; axial parenchyma diffuse or diffuse-in-aggregates; pollen monosulcate [anasulcate], tectum reticulate-perforate [here?]; ?genome duplication; "DEAER" motif in AP3 and PI genes lost, gaps in these genes.
[AUSTROBAILEYALES [[CHLORANTHALES + MAGNOLIIDS] [MONOCOTS [CERATOPHYLLALES + EUDICOTS]]]]: phloem loading passive, via symplast, plasmodesmata numerous; vessel elements with scalariform perforation plates in primary xylem; essential oils in specialized cells [lamina and P ± pellucid-punctate]; tension wood + [reaction wood: with gelatinous fibres, G-fibres, on adaxial side of branch/stem junction]; tectum reticulate; anther wall with outer secondary parietal cell layer dividing; nucellar cap + [character lost where in eudicots?]; 12BP [4 amino acids] deletion in P1 gene.
[[CHLORANTHALES + MAGNOLIIDS] [MONOCOTS [CERATOPHYLLALES + EUDICOTS]]] / MESANGIOSPERMAE: benzylisoquinoline alkaloids +; sesquiterpene synthase subfamily a [TPS-a] [?level], polyacetate derived anthraquinones + [?level]; outer epidermal walls of root elongation zone with cellulose fibrils oriented transverse to root axis; P more or less whorled, 3-merous [?here]; pollen tube growth intra-gynoecial; extragynoecial compitum 0; carpels plicate [?here]; embryo sac bipolar, 8 nucleate, antipodal cells persisting; endosperm triploid.
[CHLORANTHALES [[MAGNOLIALES + LAURALES] [CANELLALES + PIPERALES]]]: sesquiterpenes +; (microsporogenesis also simultaneous); seed endotestal.
[[MAGNOLIALES + LAURALES] [CANELLALES + PIPERALES]] / MAGNOLIIDS / MAGNOLIANAE Takhtajan: (neolignans +); root cap meristem open; vessels solitary and in radial multiples, (with simple perforation plates in primary xylem); (sieve tube plastids with polygonal protein crystals); lamina margins entire; A many, spiral [possible position here], extrorse; ovules with hypostase, nucellar cap +, raphal bundle branches at the chalaza; antipodal cells soon die.
[MAGNOLIALES + LAURALES]: palmitol the main wax; A whorled; pollen with lamellate endexine; carpel cross-zone initiated late; ovules 1(-2)/carpel, basal, erect, apotropous; fruitlets 1-seeded.
LAURALES Berchtold & Presl Main Tree.
(Cork subepidermal); sieve tube plastids with polygonal protein crystalloids and starch; nodes 1:?; petiole bundle(s) arcuate; calcium oxalate crystals small, as sand, etc.; leaves opposite; inflorescence ± cymose; receptacle ± concave, hypanthium +; P spiral; inner staminodia +; stylulus quite long, extragynoecial compitum +; megaspore mother cells several; fruits indehiscent, hypanthium persistent/accrescent; mesotesta crushed, seed endotestal, endotesta tracheidal, tegmen crushed; embryo long; duplication of the PI gene. - 7 families, 91 genera, 2858 species.
Age. Wikström et al. (2001) suggest an age of (121-)114, 108(-101) m.y. for the beginning of divergences here, rather like nthe 108.8 m.y. in Tank et al. (2015: Table S2), while Renner (2005) thought that it began ca 130.2 m.y., Magallón and Castillo (2009: relaxed and constrained penalized likelihood datings) ages of ca 171.4 and 119.3 m.y., Bell et al. (2010) ages of (133-)119, 112(-107) m.y., Magallón et al. (2013) and Magallón et al. (2015) suggested ages of around 117.5 m.y.a. and 114.9 m.y.a. respectively and Massoni et al. (201a5) ages of (165.6-)158.9, 117.4(-112) m. years.
The young fruits of Protomonimia, in Turonian deposits from Japan that are ca 91 m.y. old, have several carpels borne in spirals on a concave axis; there is a stigmatic crest. The young seeds have a thick testa, the exotesta being palisade and with sinuous anticlinal cell walls (Nishida & Nishida 1988). If a member of Laurales, it would probably be assigned to stem Laurales if only because there are several ovules/carpel. For Cecilanthus, from early Cenomanian Maryland ca 100 m.y.a., see Herendeen et al. (2016) and above).
Note: Boldface denotes possible apomorphies, (....) denotes a feature common in the clade, exact status uncertain, [....] includes explanatory material. Note that the particular node to which many characters, particularly the more cryptic ones, should be assigned is unclear. This is partly because homoplasy is very common, in addition, basic information for all too many characters is very incomplete, frequently coming from taxa well embedded in the clade of interest and so making the position of any putative apomorphy uncertain. Then there are the not-so-trivial issues of how character states are delimited and ancestral states are reconstructed (see above).
Evolution: Divergence & Distribution. See Renner (1999, 2005a) for details of diversification within Laurales. Soltis et al. (2005b) summarize information on possible synapomorphies for the clade (see also Staedler et al. 2009); von Balthazar et al. (2011) map the distributions of many characters in the order while Doyle (2009) placed variation in exine infratectum morphology on the tree. An extragynoecial compitum is common in Laurales, and it could be considered an apomorphy for the order, and then it would have to be lost at least twice and regained once, or acquired independently several times (see e.g. Endress & Igershein 2000; Endress 2001a).
Pollination Biology & Seed Dispersal. Although at one level the order is uniform in gynoecial mophology, the carpel(s) usually being free, there is considerable diversity in the ways in which the pollen tube reaches the ovule (Endress & Igersheim 1997 and references), a diversity not captured even in Armbruster (2002).
Genes & Genomes. Oginuma and Tobe (2006) suggest that the base chromosome number for Laurales is x = 11.
Chemistry, Morphology, etc. Isorhamnetin occurs in Lauraceae, Gomortegaceae and "Monimiaceae" (Crawford et al. 1986). Flowers that are white around the periphery and coloured in the centre are scattered throughout the clade (Calycanthaceae, Atherospermataceae, etc.).
The apex of the nucellus in some Atherospermataceae, and perhaps also in Siparunaceae and Calycanthaceae, is exposed (Endress & Igersheim 1997). Little is known of obturator presence in the order, and of many other embryological details, although Endress (1972a) suggests there is considerable variation, some of which may link nicely with phylogeny.
See also Eklund (1999) for general information, Benzing (1967a, b), for nodes, Metcalfe (1987) for vegetative anatomy, Endress (2011a) for the distribution of an extragynoecial compitum, and Kimoto and Tobe (2001) for embryology.
Phylogeny. Calycanthaceae are sister to other members of the clade in just about all studies, but some other interfamily relationships remain unclear. [Siparunaceae [Gomortegaceae + Atherospermataceae]] form a moderately-supported clade, relationships between the last two being supported strongly in D. Soltis et al. (2000, 2011; see also Massoni et al. 2014), although Glossocalyx was weakly supported as sister to all Laurales bar Calycanthaceae in Massoni et al. (2015a: add. file 2). [Monimiaceae + Lauraceae + Hernandiaceae] form another clade. Although sister-group relationships between Lauraceae and Hernandiaceae had no support (D. Soltis et al. 2000), in a morphological study the clade [Hernandiaceae + Lauraceae] has strong support (Doyle & Endress 2000, see also Renner & Chanderbali 2000). However, the comprehensive molecular studies of Massoni et al. (2014, 2015a) found some support for the clade [Monimiaceae + Lauraceae]; Tank et al. (2015: Table S2, 91.1 m.y., Laur. 93) found a [Hernandiaceae + Monimiaceae] clade. The [Monimiaceae + Lauraceae + Hernandiaceae] clade is one of the few cases where there seems to be persistent disagreement between morphology and molecules (Renner & Chanderbali 2000). Here I follow morphology (see also Renner et al. 1997 and Renner 1998, 1999, esp. 2005a).
Classification. The contents of Cronquist's (1981) Laurales and Takhtajan's (1997) Lauranae are largely the same as Laurales as they are circumscribed here.
Thanks. I am grateful to S. Renner for comments.
Includes Atherospermataceae, Calycanthaceae, Gomortegaceae, Hernandiaceae, Lauraceae, Monimiaceae, Siparunaceae.
Synonymy: Atherospermatales Martius, Calycanthales Link, Gyrocarpales Dumortier, Hernandiales Martius, Illigerales Martius, Monimiales Berchtold & Presl - Lauranae Takhtajan - Calycanthidae C. Y. Wu, Lauridae C. Y. Wu - Lauropsida Horaninov
CALYCANTHACEAE Lindley Back to Laurales
Deciduous or evergreen shrubs to trees; tryptamine [calycanth(id)ine] alkaloids +; primary stem ± with vascular cylinder; cortical bundles +, inverted; vessel elements with simple perforation plates; sieve tube plastids also with peripheral protein fibres; pericyclic fibres 0; nodes 1:2 [see below]; petiole bundle arcuate, with wing bundles; hairs unicellular; buds perulate, (terminal bud aborts); lamina vernation flat to curved; flowers large [³3 cm across], (terminal); receptacle with cortical vascular system; P many, spiral; A with prolonged connective, nectariferous staminodes ³10; (pollen grains tricellular); stigma dry; suprastylar extragynoecial compitum +; ovule micropyle exostomal, outer integument 6-15 cells across, inner integument 4-5 cells across, hypostase +; embryo sac long; fruits ± achenes; testa multiplicative, exotestal cells cuboid, slightly lignified; endosperm diploid, development autonomous [lacking paternal contribution]; n = 11.
5[list]/11 - two groups below. East Asia, North America, N.E. Australia (map: from Wu 1983; Endress 1983; Hong 1993; Fl. N. Am. III 1997; Qian & Ricklefs 2004). [Photo - Fruit © Robert Kowal, Flower.]
Age. Crown group Calycanthaceae have been dated to as recently as the early Eocene (60-)52, 49(-41) m.y.a. (Wikström et al. 2001) or back in the Campanian, ca 110 m.y.a. (Zhou et al. 2006) or (100-)98(-97) m.y.a. (Bell et al. 2010); Renner (2005) suggested an age of 56-54 m.y. while there are estimates of (119.7-)111.9, 97.9(-91.6) m.y. in Massoni et al. (2015a).
Fossils are interesting. Araipa florifera, from the Lower Cretaceous of Brasil around 113 m.y.a., has flowers that externally are very like those of Calycanthaceae, but its leaves are lobed (Mohr & Ecklund 2003); unfortunately, nothing is known of the internal structure of the flower. The late Cretaceous Virginianthus calycanthoides (98-113 m.yo., perhaps 108 m.y. - Massoni et al. 2015b) has been placed in Calycanthaceae. It has small flowers, anthers dehiscing by lateral hinges, and reticulate pollen with a single sulcus (Friis et al. 1994). Its anasulcate pollen is like that of Idiospermum, plesiomorphic for the order. Assuming the lateral hinges on the anthers of Virginianthus are equivalent to the rather differently oriented hinges found in most other taxa (c.f. also those of Sinocalycanthus - parallelism?), hinged anthers may be a synapomorphy for Laurales, and anthers with slits a synapomorphy for crown-group Calycanthaceae. However, the phylogenetic position of Virginianthus has been questioned, and whether it is in Calycanthaceae, sister to Calycanthaceae (e.g. Doyle & Endress 2010), sister to all other Laurales, or perhaps not to be included in Laurales at all, is unclear (Eklund 1999; Crepet et al. 2005; Zhou et al. 2006; Doyle & Endress 2007; Doyle et al. 2008b), although the latter idea is least likely. See also Friis et al. (2011) for fossils.
The rather younger (Turonian, ca 85.8 m.y. old - see Massoni et al. 2015b) Jerseyanthus is more certainly Calycanthaceae and may even be sister to Calycanthus; it has the same distinctive disulcate pollen (Crepet et al. 2004, 2005). However, Jerseyanthus is remarkable in having flower parts in the sequence petal-like tepal (outside) - introrse staminode - extrorse stamen - abaxially curved "petal-like staminode" - pistillode (inside), an arrangement of parts quite unlike that of any other living angiosperm, although Staedler et al. (2007) interpret the outer staminode series as being inner tepals.
1. Idiospermoideae Thorne
Flavonols 0, but luteolin, etc. +; (vessel elements with scalariform perforation plates); A 10-20, almost P like, thick, subsessile; G 1-2(-5), style 0, stigma stout, fleshy, extragynoecial compitum +; ovules (2/carpel), outer integument 12-15 cells thick, nucellar beak +; seed large [³3 cm across], cotyledons (3-)4, peltate.
1/1: Idiospermum australiense. Queensland, Australia.
Synonymy: Idiospermaceae S. T. Blake
2. Calycanthoideae Burnett
(P 10³); A 5-20, filaments rather slender, (anthers valvate [H-dehiscence] - Sinocalycanthus), (staminodes 0); pollen equatorially and vertically disulcate; G ³5, carpellary vascular supply recurrent [Calycanthus], stigma filiform, compitum by style coherence; outer integument 5-6(-8) cells thick; (>1 embryo sac/ovule); cotyledons spirally twisted; (n = 12).
4/10. China, Korea, Taiwan, North America.
Age. Renner (2005) suggested an age of 33-24 m.y. for crown-group Calycanthoideae.
Synonymy: Butneriaceae Barnhart, Chimonanthaceae Perleb
Evolution: Divergence & Distribution. Massoni et al. (2015a) suggest that there has been a major slow-down of diversification in this clade.
For possible apomorphies of the two subfamilies in addition to those suggested above, see Staedler et al. (2009).
Pollination Biology & Seed Dispersal. Gottsberger (2016) summarized pollination in the family. Nectar or food bodies are produced by the tepals and the latter sometimes by the stamens, although neither in Idiospermum.
For a suprastylar extragynoecial compitum, see Endress and Igersheim (1997).
Genes & Genomes. Isozyme duplication in Calycanthus suggests that there has been ancient polyploidy here (Soltis & Soltis 1990).
Chemistry, Morphology, etc. The two rings of vascular tissue in the stem are quite distinct from the seedling stage onwards. The leaf is innervated by paired traces from the inner vascular ring which very soon fuse and form the median petiole bundle, and by two traces from the cortical bundles that form the lateral or wing bundles (Balfour & Philipson 1962; Benzing et al. 1967; Beck et al. 1982), however, I could not see these central paired traces in Chimonanthus (stem too old?). Odd teeth are sometimes found on the lamina of Calycanthus virginianus, at least on the plant in my back garden.
Calycanthus occidentalis has inverted recurrent vascular bundles in the hypanthium, perhaps evidence of receptacular epigyny (Dengler 1972). Staedler et al. (2007a) note that the numbers of floral parts, tepals, stamens, staminodes, etc., are more or less Fibonacci numbers (3, 5, 8, 13,....). The carpels in general are more or less plicate. The ovules of Calycanthus almost lack parietal tissue, but they do have a nucellar cap (Dahlgren 1927). The seeds are poisonous and have characteristic alkaloids.
For the morphology of Idiospermum, see Blake (1972), for chemistry, see Crawford et al. (1986). For general information on Calycanthaceae, see Nicely (1965) and Kubitzki (1993b), for the chloroplast genome, etc., see Goremykin et al. (2003b), for disulcate pollen of Calycanthus, see Albert et al. (2011), for floral development, see Rauh and Reznik (1951), for gynoecial development, see Staedler et al. (2007b).
Phylogeny. Li et al. (2004) clarify phylogenetic relationships in the family; Idiospermum is sister to the rest.
Classification. Idiospermum is a very distinctive genus and has sometimes been recognised as a separate family (e.g. Cronquist 1981). However, it is monotypic and shares many features with the other Calycanthaceae, although the alkaloids and the distribution of xylem parenchyma differ in detail.
[[Siparunaceae [Gomortegaceae + Atherospermataceae]] [Monimiaceae [Hernandiaceae + Lauraceae]]]: evergreen trees; (plants Al accumulators); vessel elements with scalariform perforation plates; hippocrepiform sclereids in pericycle; mucilage cells + [?this level]; lamina with rather distant teeth, one vein entering opaque, persistent glandular cap; flowers rather small [usu. <1 cm across], inconspicuous; A whorled, stamens with paired nectaries/glands at base, valvate, valves apically hinged; tapetum ?; pollen inaperturate, exine thin [pollen not resistant to acetolysis], infratecum intermediate, surface ± spinulose, intine thick, outer part with radial channels; carpel development?; funicular vascular bundle not branching in chalaza; fruit fleshy, (splitting irregularly).
Age. This clade can be dated to (103-)96, 89(-82) m.y.a. (Wikström et al. (2001) and fossil-based estimates are ca 91 m.y. (Crepet et al. 2004) - note the topology in both; Renner (2005) suggested an age of around 127 m.y.a., ca 107.9. m.y.a. is the age in Magallón et al. (2015) and (157.7-)147.6, 82(-38.5) m.y. is that in Massoni et al. (2015a).
Fossils of Lovellea wintonensis, from the upper Albian of Queensland, Australia, have characters suggesting Laurales, although they do not suggest any particular family; morphological cladistic analyses place it somewhere around here (Dettmann et al. 2010). It has disulcate pollen (see Calycanthaceae-Calycanthoideae!), an inferior ovary, partly fused carpels with long styluli, the ovule has a hypostase, and the seed has two layers of cells, the inner being made up of transfer cells, each including a crystal; it lacks staminodes (Dettmann et al. 2010). Dettmann et al. (2010) compare Lovellea wintonensis with Gomortega (Gomortegaceae) and Tambourissa (Monimiaceae) in particular, i.e. with taxa on both branches of this clade (see also Massoni et al. 2015b: age ca 100 m.y.).
Evolution: Pollination Biology & Seed Dispersal. Nectar is secreted by the paired glands at the base of the stamens/staminodes, although when the hypanthium is well developed they are lost (Erbar 2014 and references; Gottsberger 2016).
Chemistry, Morphology, etc. Leitão et al. (1999) summarize alkaloid distribution in Monimiaceae in the old sense, which includes Atherospermataceae, Monimiaceae s. str., Siparunaceae and sometimes even Hernandiaceae.
Staedler and Endress (2009) discuss floral phyllotaxis; there is considerable variation, with both whorled and spiral phyllotaxis in all families that are not monotypic, phyllotaxis even varying within a species. For variation in exine structure in this part of the tree, the pollen of many taxa having an infratectum that is more or less intermediate between granular and columellar, see Doyle (2009). For discussion as to what the nectary glands "are", whether stipules, staminodes, or structures arising de novo, see e.g. Sampson (1969b). How they are vascularized is quite variable (Kasapligil 1951; Sampson 1969b). The ovule is median, developing on on early-initiated cross-zone; Endress and Doyle (2015) note that carpel development in this clade in intermediate between plicate and ascidiate.
There is little information on tapetal development and most other embryological details and of seed anatomy; this is especially true of the first three families (Kimoto & Tobe 2001 for a summary). See Doyle (2007) for leaf teeth and Hesse and Kubitzki (1983) for pollen ultrastructure. For information on Monimiaceae and the other families previously included in them, see Schodde (1970), Philipson (1993), Sampson (1993, 1997, 2007) and Foreman and Sampson (1987: pollen), Romanov et al. (2007: fruit anatomy) and Kimoto and Tobe (2008b: embryology).
[Siparunaceae [Gomortegaceae + Atherospermataceae]]: acicular crystals +; hypanthium closed by roof; anthers bisporangiate, monothecal, pollen with columellar infratectum; embryo very small, endosperm copious.
Age. Renner (2005) suggested an age of 124-118 m.y., Tank et al. (2015: table S1, S2) an age of ca 98.4/97 m.y., and Magallón et al. (2015) an age of ca 91.8 m.y.a. for this node.
Crepet et al. (2016) assign Jamesrosea to stem [Gomortegaceae + Atherospermataceae]; found in Burmese amber ca 98 m.y.o. it suggests a rather different biogeographic history than do the distributions of extant taxa, all southern/Gondwanan.
SIPARUNACEAE Schodde Back to Laurales
Shrubs or lianes; plants Al accumulators; indumentum often stellate; vessel elements also with simple perforation plates; no hippocrepiform sclereids in pericycle; primary stem?; nodes 1:1; petiole bundles flattened-annular, (medullar plate +); cuticle wax?; buds not perulate; lamina vernation curved-conduplicate, (margins entire); plants monoecious or dioecious, flowers imperfect; hypanthium well developed; (flowers monosymmetric - Glossocalyx); P 4-6(-7) or obscure, (connate, lingulate); A (1-)2-many [e.g. 2 + 2 + 2], anthers often with one flap, paired glands 0, nectar 0; tapetum glandular; G 3-many, occluded by secretion as well, stylulus short; styles postgenitally united in receptive zone; ovule unitegmic, integument 3-5(-?8) cells across, hypostase +; megaspore mother cells several, megaspores elongating [Siparuna], embryo sacs several/ovule, starch-rich; hypanthium splitting irregularly in fruit, (drupelet with a fleshy appendage - "stylar aril"); (seeds bilaterally flattened - Glossostigma); endotegmen with reticulate thickenings; n = 22.
2[list]/75: Siparuna (74). Tropical America (Siparuna), W. Africa (Glossocalyx) (map: S. Renner). [Photo - Flower, Fruit.]
Age. Renner (2005) suggested an age of around 90 m.y. for crown-group Siparunaceae.
Evolution: Divergence & Distribution. Divergence within Siparuna may have begun ca 80 m.y.a. (Renner 2005).
Pollination Biology & Seed Dispersal. Pollination is by genera of cecidomyiid gall midges, which lay eggs mostly in staminate flowers; the larvae destroy the flower, but the female flower aborts if eggs are laid in it (Feil 1992; Renner et al. 1997; Gottsberger 2016).
Dioecy seems to have evolved several times from monoecy in Siparunaceae (Renner & Won 2001).
The fruits of Siparuna may be a particulary valuable resource for frugivores (P. Jorgensen, pers. comm.). In most taxa the hypanthium splits irregularly when the fruits are ripe, the walls spreading widely and exposing the drupelets inside. The drupelets, and/or their fleshy appendages, differ strikingly in color from the inside of the fruit (see also Monimiaceae). This fleshy appendage is called an aril by Renner and Hausner (1997) and occurs only in dioecious taxa.
Chemistry, Morphology, etc. The ovule is interpreted as having lost its outer integument by Kimoto and Tobe (2003).
General information is taken from Philipson (1993), details of embryology may be found in Heilborn (1931: very strange female embryology) and Kimoto and Tobe (2003), floral morphology in Endress (1980c), and of pollen development, etc., in Bello et al. (2002a).
Phylogeny. For phylogenetic relationships in Siparunaceae, see Renner and Won (2001).
[Gomortegaceae + Atherospermataceae]: bud scales +; sieve tube plastids also with peripheral protein fibrils; outer A alone staminodial; stylulus short.
Age. Estimates for the age of this node are (56-)51, 50(-45) and (44-)39(-34) m.y.a. (Wikström et al. 2001), (44-)29, 25(-12) m.y. (Bell et al. 2010), or (145.6-)130.5, 55(-24.4) m.y. (Massoni et al. 2015a). Other ages for the clade (?= age of stem Atherospermataceae) from 244 to 140 m.y. have been entertained (Renner et al. 2000), while Renner (2004) suggested an age of around 116-112 m.y.a.; ca 85.3 m.y.a. is the age in Tank et al. (2015: table S2) and 78.4 m.y.a. the age in Magallón et al. (2015).
Chemistry, Morphology, etc. Doweld (2001b) emphasized the similarities between Atherospermataceae and Gomortegaceae, especially the tracheoidal endotesta (perhaps plesiomorphic). Both have fruits (drupaceous, achenial) in which the seed coat would be expected to have lost its protective function.
GOMORTEGACEAE Reiche Back to Laurales
Alkaloids?, Al accumulation ?; primary stem with separate bundles; nodes 1:2; secondary phloem with flaring rays; cuticle wax?; lamina entire; flower parts between spiral and whorled, hypanthium 0; P 5-7(-9); A 7-13, tetrasporangiate, filaments rather slender; microsporogenesis modified simultaneous; ovary inferior, [2-3(-5)], style stout, branches erect, stigmatic; compitum 0; ovule apical, pendulous, hemianatropous [or straight?]; megaspore mother cell 1; fruit drupaceous; seed single [usu.], pachychalazal; ?testa/tegmen; ?embryo long; n = 21.
1[list]/1: Gomortega keule. C. Chile, rare (map: from Donoso Z. 1994). [Photo - Flower.]
Evolution. Pollination Biology & Seed Dispersal. For pollination - probably by syrphid flies - see Gottsberger (2016).
Chemistry, Morphology, etc. Vessel elements in young wood may have simple perforation plates (Metcalfe & Chalk 1987). Stern (1955) thought that nodal anatomy was unclear; here I follow Howard (in Metcalfe & Chalk 1987).
The inflorescences, often described as being racemose, have a terminal flower. Although the body of the ovule is straight, its insertion on the funicle is oblique (c.f. Endress & Igersheim 1997). Ovule development and fruit and seed anatomy would repay investigation.
Some information is taken from Kubitzki (1993b: general), Doweld (2001: seed) and Heo et al. (2004: embryology).
ATHEROSPERMATACEAE R. Brown Back to Laurales
Bisbenzylisoquinoline alkaloids +, Al accumulation 0; (hairs T-shaped); nodes 1:1; primary stem?; stomata anomocytic; lamina vernation involute [Laurelia] or conduplicate; inflorescence racemose; (flowers medium sized - ca 2 cm across); P = 2-4 + 2-4, or K 2, C 8, or K 5 + 5, C 5 (+ 5); tapetum amoeboid, cells binucleate; pollen grains polar di- or meridionally syncolpate, (tricellular), reticulate, exine infractectum columellar; G 4-many, occluded by secretion as well, (stylulus gynobasic), (none); styles postgenitally united in receptive zone; outer integument 2-3 cells across, inner integument 2-4 cells across, (nucellus apex exposed), parietal tissue ?6-8 cells across; (megaspore mother cell 1); fruit achenial, plumose, hypanthium woody; embryo also medium; n = 22, 57.
6-7[list]/16. New Guinea to New Zealand and New Caledonia, Chile, scattered (map: Philipson 1986a; Andrew Ford, pers. comm. [Australia]). [Photo - Fruit.]
Age. Divergence within Atherospermataceae may have begun ca 90 or ca 61 m.y.a. (Renner 2005) or (92.8-)79.4, 29.5(-12.6) m.y.a. (Massoni et al. 2015a).
Atherospermataceae are known from forests on the Antarctic Peninsula of the late Cretaceous/early Caenozoic; the oldest fossils are ca 88 m.y. (Poole & Francis 1999; Renner et al. 2000; Friis et al. 2011 for references).
Evolution: Divergence & Distribution. Fossil wood (?identification) of Atherospermataceae is recorded from the Upper Eocene of Germany and elsewhere in the northern hemisphere (Friis et al. 2011 for references), and distinctive pollen attributed to Laurelia is known from the lower Eocene in Europe (Hofmann et al. 2015) -c.f. Winteraceae.
Renner et al. (2000) and Renner (2004) discuss the evolution and biogeography of the family. Atherospermophyllum, from the Eocene (52.2 m.y.a.) in Patagonia, seems to be related to Australian members of the family, rather than to genera now found in South America (Knight & Wilf 2013).
Chemistry, Morphology, etc. The plants do not accumulate aluminium (Webb 1954). Atherosperma has two sepals completely enclosing the bud, and then eight petals. The vasculature of the anther glands is independent of that of the anthers (Canright 1952).
Some information is taken from Philipson (1993), Endress (1980c: flower), and Stanstrup et al. (2010: chemistry); for some ovular morphology and embryology, see Sampson (1969b, c), and for wood anatomy, see Poole and Gottwald (2001).
Phylogeny. Renner et al. (2000) suggested that the [Doryphora + Daphnandra] clade, from the Queensland-New South Wales area of Australia, was sister to the rest of the family.
[Monimiaceae [Hernandiaceae + Lauraceae]]: aporphine alkaloids and variants +; (cork cambium outer cortical); crystals +, small; A whorled; pollen exine infratectum granular; extragynoecial compitum 0; ovule apical, pendent, (micropyle bistomal).
Age. Estimates for the age of this node are (67-)52, 45(-32) m.y. (Bell et al. 2010), ca 105.1 m.y.a. (Magallón et al. 2015), ca 124 m.y. (Renner 2005), (146.2-)134.2, 59.9(-17.1) m.y. (Massoni et al. 2015a) or (134-)122(-110) m.y.o. (Michalak et al. 2010) - in the last three Hernandiaceae are sister to the rest.
The distinctive Mauldinia (see below under Lauraceae) has been placed sister to this clade in a constrained morphological analysis by Doyle and Endress (2010), and this has been dated to around 95.5 m.y.a. (Massoni et al. 2015b). Other fossils ca 108 m.y.o. have also been placed at this node (Massoni et al. 2015b).
Chemistry, Morphology, etc. See Kimoto and Tobe (2008a) for a comprehensive summary of the variation in embryology and seed of the whole group.
Phylogeny. See the above for relationships in this area, which are still unclear.
MONIMIACEAE Jussieu Back to Laurales
Also shrubs or lianes, climbing by scrambling; (plants Al accumulators); primary stem with cylinder or separate bundles; (vessel elements with simple perforation plates); wood with broad rays; nodes 1:1-7+; sieve tubes with rosette-like non-dispersive protein bodies; cuticle wax?; (stomata anomocytic); lamina vernation conduplicate, (margins entire); plants monoecious or dioecious; flowers medium-sized; A 3-many, dehiscing longitudinally, (annular), ± sessile or filaments rather slender, connective produced; tapetum glandular, cells binucleate; (pollen grains with encircling aperture); G (1-few)-many, occluded by secretion as well, stylulus short-0, stigma broad, dry; outer integument 2-3 cells across, inner integument 2-4 cells across, parietal tissue ca 8 cells across, hypostase +, funicle stout, obturator + (0); hypanthium fleshy or not, fruit drupelets; mesotesta usu. tracheidal, (endotesta not tracheidal); embryo short to quite long.
22[list]/200. Tropical-Southern Hemisphere, but esp. Australasia.
Age. Estimates for the age of crown-group Monimiaceae are (86-)78, 66(-58) m.y.a. (Wikström et al. 2001); Renner (2005a) suggest an age of around 102.5 m.y. and and Renner et al. (2010) ages of (93-)90(-87) m.y. (there are ca 85 m.y.o. old fossil woods); dates in Michalak et al. (2010) are (80-)73(-40) m.y., depending on the clock. The estimate in Bell et al. (2010) is (57-)41, 35(-21) m.y. and that in Massoni et al. (2015a) is (143-)125.7, 62.8(-39.5) m.y. ago.
1. Monimioideae Rafinesque
Lianes to trees; septate fibres 0; sieve tube plastids with starch (not Peumus); hairs often stellate; (bud scales +); plants dioecious; t to 12, inner petaloid; staminate flowers: (staminate receptacle aplitting); (anthers bisporangiate, ?thecae, dehiscing transversely - Monimia), staminodes +, (paired nectaries 0 - Palmeria); styles postgenitally united in receptive zone [?all]; hypanthium splitting irregularly in fruit, or circumscissile, endocarp massive; (drupelets with fleshy appendages); n = 39, ca 46.
3/19: Palmeria (15). Scattered: Chile, the Mascarenes, east Australia, New Guinea (Map: red, in part from Fl. Australiense 2. 2007).
Age. The crown age of Monimioideae is ca 76 m.y. (Renner 2005a) or (75-)57, 52(-34) m.y. (Renner et al. 2010).
[Hortonia + The Rest]: secondary phloem with flaring rays; septate fibres +; endocarp thin.
Age. Estimates of the age of this node are ca 100 m.y. (Renner 2005a) or (84-)71(-57) m.y. (Renner et al. 2010).
2. Hortonioideae Thorne & Reveal
Shrubs; hairs stellate; flowers perfect, ca 3 cm across; T many, spiral, inner petaloid; staminodes +; pollen with hollow, spiral sexinous strands, intine with tangential channels; G 6-14; suprastylar extragynoecial compitum; n = 19.
1/3. Sri Lanka. (Map above: green)
Synonymy: Hortoniaceae A. C. Smith
3. Mollinedioideae Thorne
Lianes, shrubs or trees; (sieve tube plastids with starch - Tambourissa); plants monoecious; (hypanthium closed by roof), (splitting in flower, stamens borne on lobes), P not differentiated, often inconspicuous to 0; (extragynoecial compitum +); paired nectaries 0 (+ - Mollinedia); (G connate, inferior - Tambourissa); styles postgenitally united in receptive zone or hyperstigma + or suprastylar extragynoecial compitum; (hypanthium splitting irregularly in fruit), (drupelets with fleshy appendages); (cotyledons 4 - Kibaropsis); n = 19 [several], 22, 36, 39, 40-43.
18/180: Mollinedia (90 [?20 - S. Renner, pers. comm.]), Tambourissa (45), Kibara (45). Tropical-Southern Hemisphere, esp. Australasia (map: from Renner et al. 2010, fossil localities in green; Jordaan & Lötter 2012, Xymalos).[Photo: Fruit, Flower, Fruit, Levieria fruit, Wilkiea fruit.]
Age. The age of this node is about 51.3 m.y. (Renner 2005a) or (58-)44(-31) m.y. (Renner et al. 2010).
Evolution: Divergence & Distribution. The separation of Monimia from its sister genus, the East Malesian Palmeria, dates to (48-)32(-16) m.y.; the former is endemic to the Mascarenes, which are a mere 15-8 m.y. old (Renner et al. 2010), so Monimia must have dispersed on to the islands from elsewhere (?Malesia). In general, there is little evidence of Gondwananan vicariance in the family (Renner et al. 2010). Interestingly, the affinities of the recently-described Monimiophyllum, from the Eocene of ca 52.2 m.y.a. in Patagonia, are to the Australian-Malesian Wilkiea clade (Knight & Wilf 2013), which has been dated to 38-16 m.y. (Renner et al. 2010).
Pollination Biology & Seed Dispersal. A variety of small insects pollinate the flowers. The floral parts may be more or less exposed or enclosed in a fig-like structure. If the flowers are enclosed, thrips (Thysanoptera) lay their eggs in young flowers, adults covered in pollen emerging when the flowers are mature (Gottsberger 1977, 2016; Philipson 1986a).
There is an hyperstigma in Tambourissa and some other genera, a remarkable condition where the pollen germinates on a mucilaginous secretion at the entrance to the hypanthium (Endress 1980c; Endress & Lorence 1983; Friis & Endress 1990), and other genera may have postgenital fusion in the stigmatic region or a suprastylar extragynoecial compitum (Endress 1980c; Endress & Igersheim 1997).
In genera like Palmeria, Tambourissa, etc., the drupelets are surrounded by a fleshy, accrescent hypanthium. This splits, exposing the fruits, and the colour of the inside sometimes forms a striking contrast with that of the drupelets.
Plant-Animal Relationships. Papilio dardanus caterpillars have been found on Xymalos (Jordaan & Lötter 2012); see also Lauraceae.
Chemistry, Morphology, etc. Decaryodendron has flowers with up to 1000 carpels, and flowers of Tambourissa have up to 2000 carpels. Mollinedia has carpels that are initially unsealed, but are later occluded by secretion; it also has a whorled perianth. Since the ovules are initiated on the cross-zone, in their apical position they have effectively been inverted 180o.
For the embryology of Hedycarya, see Sampson (1969a), for Malagasy taxa, see Lorence (1985), for floral development, see Endress (1980b: but Hortonia neither notably intermediate nor archaic, 1980c), von Balthazar et al. (2011), for wood anatomy, see Poole and Gottwald (2001), and for fruit anatomy, see Romanov et al. (2007).
Phylogeny. A [Peumus [Palmeria + Monimia]] clade is sister to the rest of the family (Renner 2002 and references), Hortonia is isolated (see also Massoni et al. 2014), but then relationships are unclear, although the monotypic Xymalos, the only mainland African member of Monimiaceae, is likely to be sister to the remainder. Fruit anatomy correlates quite well with phylogeny, e.g., Monimioideae have a massively thick endocarp, alone in the family (Romanov et al. 2007).
Classification. The three subfamilies recognised above help link with previous classifications of Monimiaceae s.l. (see below).
Previous Relationships. Only three of the subfamilies (Monimioideae, Hortonioideae and Mollinedioideae) of Monimiaceae as circumscribed by Money et al. (1950), Cronquist (1981), and Takhtajan (1997) are included here; for the rest of the family, see Siparunaceae and Atherospermataceae.
[Hernandiaceae + Lauraceae]: primary stem ± with vascular cylinder; vessel elements with simple perforation plates; hippocrepiform cells in pericycle?; leaves spiral, lamina margins entire, (lobed); (heterodichogamy +); P whorled; (filaments slender); tapetum amoeboid; microspore mother cells in single layer; pollenexine thin, spines set in a reduced granular layer, intine very thick, outer layer with a radially oriented microfibrillar structure; G 1, inferior, stylar canal 0, stigma dry; compitum necessarily 0; ovule pachychalazal, outer integument ³4 cells across, (nucellus apex exposed), hypostase 0; embryo sac more or less linear; testa thick, multiplicative; endosperm 0; germination epigeal.
Age. Ca 91.2 m.y.a. is the age for this node in Magallón et al. (2015).
The fossil Mauldinia (see below) may best be placed here, rather than within Lauraceae (Doyle & Endress 2007). Bandulskaia, from the Early Eocene of Tasmania and identified as Lauraceae based on several distinctive epidermal features, has huge leaf teeth 2000+ µm long that lack the glandular cap of teeth of other Laurales; if the fossil is correctly identified, independent origin of these teeth is likely (Carpenter et al. 2007). Cohongarootonia (it has a hollow style) and perhaps Powhatania, both from Early-Middle Albian sediments 125-118 m.y. old in Virginia, probably belong in this general area (von Balthazar et al. 2011).
Evolution: Divergence & Distribution. For additional possible synapomorphies, see Doyle and Endress (2000). A scenario for ovary evolution is that it became inferior in the common ancester of Hernandiaceae and Lauraceae, being lost (?more than once) in the latter family, but other scenarios are about equally parsimonious. Protrusion of the embryo sac from the nucellus may ultimately go here, too.
Pollination Biology. Rohwer (2009) compares the heterodichogamous flowers (two morphs - in one the flowers discharge pollen first, in the other, the stigma is receptive first) of Lauraceae with those of Hernandiaceae (for Hernandia, see Endress & Lorence 2004) and suggests that heterodichogamy may be common to the two families. He interprets the floral morphology of Hernandiaceae from this point of view.
Chemistry, Morphology, etc. For the distinctive pollen of these two families, see Kubitzki (1981).
HERNANDIACEAE Blume Back to Laurales
Trees or lianes; hippocrepiform sclereids in pericycle?; nodes 1:3-9; petiole bundles horizontally [Valvanthera] or vertically elliptic; (stomata anomocytic); branching from previous flush; lamina venation ± palmate; breeding systems very diverse; flowers (3-)4-5-merous; P 3-10; A 3-5(-7); (nectaries outside A, 0, or much reduced); ovary inferior, usu. facing abaxially, stigma peltate; ovule micropyle variable, endostome lobed, outer integument 9-23 cells across, inner integument 3-8 cells across; fruit dry, (a samara).
5[list]/55 - two subfamilies below. Pantropical.
Age. Crown-group Hernandiaceae are about 120 or 96 m.y. (Renner 2005), (130-)112(-89) m.y.o. (Michalak et al. 2010, c.f. abstract) or (137.7-)120.2, 64.4(-35.7) m.y. (Massoni et al. 2015a).
1. Hernandioideae Miquel
(Climbing by twining petioles); Al accumulation?; glandular hairs in leaf epidermis; plant heterodichogamous; inflorescence thyrsoid; (bracteoles connate); anther valves laterally hinged; tapetal cells radially elongated; pollen grains 90-160 µm across; parietal tissue 6-8 cells across, nucellar beak +, suprachalazal nucellus massive; bracteoles accrescent in fruit [not Illigera]; (seeds ruminate - usu. Hernandia), testa vascularized, spongy, tanniniferous, walls unthickened, mesotesta massive, 7-17 cells across; n = 18, 20.
3/44. Tropical, esp. Madagascar and Indo-Malesia (map: from Kubitzki 1969; van Balgooy 1975; Trop. Afr. Fl. Pl. Ecol. Distr. 1. 2003). [Photo - Hernandia Flower, Fruit, Illigera Flower, Fruit.]
Age. The age of crown-group Hernandioideae is around 72 or 58 m.y. (Renner 2005) or about 76 m.y. (Michalak et al. 2010).
Synonymy: Illigeraceae Blume
2. Gyrocarpoideae J. H. Balfour
Stomata anomocytic; cystoliths +; leaves with strong higher-order vein areolation; inflorescence dichasial, ebracteate; flowers very small; P uniseriate; microspore mother cells?; pollen grains 19-45 µm across; ovule with nucellar cap; embryo sac protruding from nucellus; cotyledons contortuplicate [= much folded!]; n = 15.
2/10. Pantropical, esp. America (map: from Kubitzki 1969; van Balgooy 1975; Trop. Afr. Fl. Pl. Ecol. Distr. 1. 2003).
Age. Crown-group Gyrocarpoideae are 80 or 57 m.y.o. (Renner 2005) or (102-)72(-43) m.y.o. (Michalak et al. 2010).
Synonymy: Gyrocarpaceae Dumortier
Evolution: Divergence & Distribution. Michalak et al. (2010) suggested that the distribution of the family might initially have been affected by pre-drift continental arrangements, but that there had been much subsequent dispersal.
Chemistry, Morphology, etc. Some 128 alkaloids assignable to 17 different structural types have been found in the family; about half of them are aporphine alkaloids (Conserva et al. 2005; see also J.-J. Chen et al. 2011). Their distributions show no obvious correlation with phylogeny.
For floral morphology in Hernandia, see Endress and Lorence (2004); see Heo and Tobe (1995) and Kimoto and Tobe (2008) for embryology, etc., and a nice summary in the latter. Some information is also taken from Kubitzki (1969, 1993b).
LAURACEAE Jussieu Back to Laurales
Flavones, 5-O-methyl flavonols, polyketides [acetogenins], (tryptamine alkaloids) +, (plants Al-accumulators); wood often fluorescing; (secondary phloem stratified); nodes 1:2, 1:3; also crystals and crystal sand +; (stomata anomocytic); buds perulate (naked); branching ± whorled, from current flush; lamina often glaucous below, vernation conduplicate or supervolute, secondary vains usually ± steeply ascending, higher-order vein areolation strong; plants heterodichogamous; inflorescence umbellate to thyrsoid; hypanthium often short, T 3 + 3 (2 + 2; K + C), all members with three vascular bundles; A 3 [introrse] + 3 [introrse] + 3 [extrorse], with glands, three vascular bundles, sporangia widely separated on broad connective, tapetal cells 2(-4) nucleate; (microsporogenesis simultaneous); (pollen monosulcate); (stylulus 0), stigma also capitate; outer integument 3-5(-11) cells across, inner integument 2-4 cells across, parietal tissue 5-7 cells across; megaspore mother cells usu. 1; fruit a drupelet [endocarp palisade] or berry, pedicels (and tepals) often thickened and coloured; (seed ruminate), testa vascularized or not, often multiplicative, (exotestal cells cubic), (palisade), endotestal cells longitudinally or transversely elongated, with helical thickenings; endosperm nuclear; n = (11-)12, chromosomes 1-5 µm long.
Ca 50[list]/2500. Pantropical (temperate), lowland to montane. An appreciable part of the distributional area of the family, e.g. in most of West Australia, is attributable to Cassytha alone (map: from Heywood 1978; modified as in Richter 1981; Fl. N. Am. III 1997; Trop. Afr. Fl. Pl. Ecol. Distr. 1. 2003; FloraBase 2005; Cassytha, The Parasitic Plant Collection).
Age. Chanderbali et al. (2001: c.f. calibration, 682±105 m.y.!) suggested an age of 174±32 m.y. for the family, but other estimates are as young as (93-)61(-26) m.y.a. (Michalak et al. 2010); (146.6-)135.3, 66.7(-46) m.y. is the range in Massoni et al. (2015a: note topology).
Potomacanthus lobatus, provisionally assigned to Lauraceae although with an unusual combination of floral characters - there are only two whorls of stamens and no nectaries/glands - has been described from deposits in Virginia some 112-105 m.y. old (von Balthazar et al. 2007).
1. Hypodaphnideae Reveal
Tapetum?; staminodes 0.
1/1: Hypodaphnis zenkeri. Tropical West Africa.
Age. The age of 174 ± 32 m.y. for this node was proposed by Chanderbali et al. (2001).
[Cryptocaryeae [Cassytheae [[Caryodaphnopsis + Neocinnamomum] [Cinnamomeae, etc.]]]]: subsidiary cells of paracytic stomata envelop the guard cell both above and below, the guard cells having outer and inner cuticular ledges; (plant dioecious), 3 (4-several) whorls of stamens; tapetum glandular; pistillate flowers: staminodes + [= third whorl of stamens]; embryo sac protruding from nucellus; fruit type?
Age. Chanderbali et al. (2001) proposed an age of 158 ± 31 m.y. for this node, ca 98 m.y. is the age in L. Li et al. (2016).
2. Cryptocaryeae Nees
(Stamens in two, one whorls), (fourth whorl +, staminodial, with three vascular bundles [Cryptocarya]), (anthers bisporangiate by sporangial fusion); pollen surface ± verrucate; (ovary superior); fruit a berry; (n = 15 - Eusideroxylon, Endiandra).
6/710: Cryptocarya (350), Beilschmiedia (250), Endiandra (80). Pantropical, some subtropical, to New Zealand.
Age. The age of this node may be ca 82 m.y. (Renner 2005).
[Cassytheae [[Caryodaphnopsis + Neocinnamomum] [Cinnamomeae, etc.]]]: ?
Age. The age for this node (as [Cassytha + Cinnamomum]) is estimated to be (118.4-)77.3(-33) m.y. by Naumann et al. (2013).
3. Cassytheae Dumortier
Parasitic herb; flowers ± sessile; outer T small, with one trace; anthers bisporangiate, ?thecae, (fourth whorl +, staminodial, with three vascular bundles); pollen surface ± verrucate to spinuloid; micropyle bistomal, nucellar cap 0, pachychalaza 0; megaspore mother cells several, >1 embryo sac/ovule; endosperm cellular, +; chromosomes to 7 µm long.
1/16. Tropics, warm temperate regions in Australia - see The Parasitic Plant Collection. [Photo - Parasite.]
Synonymy: Cassythaceae Lindley, nom. cons.
[[Caryodaphnopsis + Neocinnamomum] [Cinnamomeae, etc.]]: ovary superior.
Age. Chanderbali et al. (2001) suggest an age of 142 ± 24 m.y. for this node.
4. [Caryodaphnopsis + Neocinnamomum]
(Abaxial leaf epidermal cells variously papillate); anthers tetrasporangiate; pollen surface smooth to verrucate.
2/21. Central and South America, South East Asia to the Philippines and Borneo.
5. Cinnamomeae Nees, Laureae Maout & Decaisne, etc. [Lauroideae Burnett / core Lauraceae]
(Plant deciduous); (cork pericyclic - Cinnamomum); (vessel elements with scalariform perforation plates); (leaves opposite); (plant dioecious); (flowers 2-merous - Potameia); (T in three or more whorls), (inner T with one vascular bundle - Umbellularia); (anthers bisporangiate - Cinnamomum), (anthers of third whorl introrse), (fourth whorl +, staminodial), (paired nectaries/glands 0 - Mezilaurus clade); tapetum amoeboid, cells 4 nucleate; micropyle exo- or bistomal, embryo sac not protruding.
Ca 40/1730: Ocotea (350), Litsea (?400), Persea (200), Cinnamomum (350: cinnamon), Lindera (100), Nectandra (90). Pantropical (temperate). [Photos - Flower, Fruit.]
Age. The age of the node (Cinnamomum, Sassafras) is estimated to be (43-)37, 32(-26) m.y. (Wikström et al. 2001) or ca 90 m.y. (Chanderbali et al. 2001) or ca 60 m.y. (L. Li et al. 2016), that of the Persea-Cinnamomum clade late Palaeocene ca 59 m.y.a., Cinnamomum and Laureae split (69.3-)56(43.2) m.y.a., and Cinnaomum s.l. itself started to diversify (60.1-)46.5(-34.2) m.y.a. (J. Huang et al. 2015).
Synonymy: Perseaceae Horaninow
Evolution: Divergence & Distribution. Lauraceae have a very rich fossil record (Friis et al. 2011) and are prominent in Mid to Late Cretaceous floras. Some taxa have odd character combinations (Takahashi et al. 2014: esp. fig. 5). Early Cenomanian Mauldinia mirabilis, ca 100 m.y. old (Drinnan et al. 1990; Viehofen et al. 2008), has remarkable inflorescences in which the lateral units are flattened and bilobed, bearing sessile flowers on their adaxial surfaces. The flowers are very like those of extant members of the family (see also Crepet et al. 2004; Friis et al. 2006b, 2011 for references), but the 2-ranked bracts/prophylls of the inflorescence units are a distinctly unusual feature. Dispersed flowers of Perseanthus some 90 m.y.o., were compared with Perseeae, and although they lacked anthers, there was associated pollen (Herendeen et al. 1994). Atkinson et al. (2015) evaluate the flowers of fossils assigned to Lauraceae.
Wood very similar to that of sassafras and named Sassafras gottwaldii is known from the Late Cretaceous at 60o S on the Antarctic Seymour Island ca 83 m.y.a. (Poole et al. 2000), but perhaps fortunately it is considered to be an example of convergence (Nie et al. 2007: stem Sassafras ca 33 m.y.o.!). The Upper Cretaceous Marmarthia, identified as Lauraceae, has leaf blades with palmate venation; the margins are lobed or perhaps toothed (Peppe et al. 2007). Labandeira et al. (2002b) assigned many fossil leaves from the earliest Caenozoic of North America to extant genera of Lauraceae.
Tank et al. (2015) suggested that an increase in net diversification somewhere around here might be linked to a genome duplication of the [Magnoliales + Laurales] node; stem Lauraceae were estimated to be some 93 m.y.o. (Tank et al. 2015: Table S1, but c.f. topology). Diversification in the family may be as recent as (93-)61(-26) m.y.a. (Michalak et al. 2010), although ages were rather uncertain there. Calibrations in Chanderbali et al. (2001) were based on continental drift events, effectively assuming what is to be proved (Gondwanan/vicariance shaping of initial divergences of the family); a crown group age for Lauraceae of (787-)682(-577) m.y. (not followed here!) was based on a vicariance event in the Ocotea complex, another (dates above) assumed a Gondwanan origin for the Chlorocardium-Mezilaurus clade, the crown-group age of [[Chlorocardium-Mezilaurus] [Alseodaphne, etc.]] being around 90 m.y. ago. These ages have been used as calibration points by Nie et al. (2007: in part) and Huang et al. (2015).
The Macaronesian Persea indica is part of a New World clade, and sister (but with rather poor support) to this clade is another Macaronesian member of the family, Apollonias barbujana also sister to New World Persea (Rohwer et al. 2009). These distributions have been explained by vicariance events as the North Atlantic opened 120-100 m.y.a. (Grehan 2017). Diversification in the speciose New World Ocotea is likely to have been rather recent (Renner 2005a), although our understanding of relationships in this area is at present too poor to worry about this.
An understanding of evolution in Lauraceae depends on a more stable and better resolved phylogeny than we have at present. Kimoto et al. (2006) noted that a minor change on the tree that they used would mean that a glandular anther tapetum and possibly also protruding embryo sac arose on a single clade and did not reverse, however, they thought that characters like a glandular tapetum and an embryo sac protruding from the nucellus arose in parallel. Indeed, in the topology suggested by Rohwer and Rudolph (2005, not cited by Kimoto et al. 2006) these characters appear in all (glandular tapetum) or most (protruding embryo sacs) members that have been examined on three successive branches of the tree, but are not, or only very rarely, found in the Mezilaurus group and other core Lauraceae ("The Rest" above). Thus there may have been reversal/loss of these characters in other Lauraceae; protruding embryo sacs are also found in at least some Hernandiaceae-Gyrocarpoideae. I have optimised these and some other characters (see von Balthazar et al. 2007) in the context of a the phylogeny of Lauraceae suggested by Rohwer and Rudolph (2005: see below). However, where many of these characters will end up on the tree is very uncertain; the topology is uncertain and our basic understanding/sampling of the morphological variation is poor.
Ecology & Physiology. The family is prominent in the lowland tropical rainforests of South East Asia-Malesia and America, much less so in Africa. In tropical montane forests in South America it may be the most speciose family (Gentry 1988) while is the second most speciose family represented by plants with stems 10 cm or more d.b.h. in Amazonian forests in general, although it has only 4/227 of the common species there (ter Steege et al. 2013). Species of Nectandra growing together on Barro Colorado island show considerable differences in their foliar secondary chemistry, the differences being implicated in defence against herbivores, and in this they are like a number of other taxa that grow in swarms of ecologically similar species in LTRF (Sedio et al. 2017). Eusideroxylon zwageri dominates (or used to - it has been heavily logged) several thousand square kilometres of West Malesian forests (Hart et al. 1989), while Litsea is one of the five most diverse genera in West Malesian l.t.r.f. (Davies et al. 2005).
Pollination Biology & Seed Dispersal. Pollination, usually rather generalist, is summarized by Gottsberger (2016). The basic mode of flowering in the family may be heterodichogamy or dianthesis. Here, plants are of two types, and one plant will be in the staminate phase while the other is in the carpellate phase, and vice versa. The staminodes produce nectar when the plant/flower is in the carpellate phase and the staminal glands of the third staminal whorl produce nectar when the plant/flower is in the staminate phase (Rohwer 2009, see also above).
Dispersal of the fruits is by birds in particular, specialized frugivores for the most part. The seeds are relatively large, and the pericarp, although thin, is nutritious, and Lauraceae are major components of birds' diets in South America and Southeast Asia-Malesia in particular; in in some ways, Lauraceae are like figs, providing a supply of food throughout the year, but of higher quality than figs (Snow 1981; Wheelwright 1986).
Bacterial/Fungal Associations. Raffaelea lauricola, an ophiostomatalean ambrosia fungus, causes laurel wilt, a serious disease of wild and cultivated Lauraceae in the S.E. U.S.A.; its insect vector is the scolytid weevel Xyleborus glabratus (Huler & Stelinski 2016).
Genes & Genomes. Both isozyme duplication and stomatal size increase over time suggesting ancient polyploidy in this clade (Soltis & Soltis 1990; Masterson 1994). Is the base chromosome number 6?
Chemistry, Morphology, etc. Lindera, at least, has distinctive C10, C12 and C14 monounsaturated fatty acids in its seeds (Badami & Patil 1981). Vestured pits are apparently absent; rays alone may be storied (Metcalfe 1987: P. van Rijckevorsel [pers. comm.] clarified reports of vestured pits and wood storying in the family). Distinctive paracytic stomata in which the subsidiary cells almost envelop the very small guard cells, the latter having outer and inner cuticular ledges, may be an apomorphy for all Lauraceae except Hyphodaphnis (Carpenter et al. 2007), however, Nishida and van der Werff (2007) found more conventional stomata in at least some Lauraceae other than Mezilaurus (for stomata, see also Hill 1986). Indeed, from a surface view it may seem as if the stomata are anomocytic, the guard cells being totally obscured. Zeng et al. (2014) described the distinctive papillate cells of the lower epidermis of Caryodaphnopsis; the apex of the papilla may be expanded and more or less fused with the apices of adjacent papillae and the stalk may be transversely septate; some Neocinnamomum and a few other Lauraceae also have papillate lower epidermides.
It has been suggested that the perianth in Lauraceae represents modified bracts, "bracteotepals" (see Ronse Decraene 2008), or, largely on the basis of gene expression in Persea, modified stamens, "androtepals" (Chanderbali et al. 2004, 2006); see also Warner et al. (2009) for the literature. Both the tepals and the stamens of Persea have three traces (Reece 1939: the ovule is anatropous!). However, other reports suggest that the stamens have single traces, even if both whorls of tepals have three traces (Laurus) or one trace in the inner whorl alone (Umbellularia: Kasapligil 1951). Sajo et al. (2016) conveniently summarize the literature - what "are" stamens with more than a single vascular trace? There are a few multistaminate Lauraceae, and other with fewer than 9 stamens because stamen whorls have been lost (Rohwer 1993a). Both extrorse and introrse anthers can occur in the same flower, although the extrorse condition seems to be developmentally derived (Buzgo et al. 2007). Dahlgrenodendron has remarkable striate pollen grains with exine, columellae, etc., while the spinules on the pollen surface found in many Lauraceae are often spirally ridged (Rai & van der Werff 1988; van der Merwe et al. 1990). The orientation of the single carpel varies (Ronse de Craene et al. 2010 and literature). Sastri (1963) and Kimoto et al. (2006) summarize embryological findings in Lauraceae; there is some discussion as to whether there is one or several megaspore mother cells. Variation in the anatomy of the pericarp, development of the cupule in fruit, etc., is summarized by Little et al. (2009). The testa is not always multiplicative. Kasapligil (1951) described a tracheidal endotegmen at the radicular end of the seed.
General information is taken from Rohwer (1993a) and Kasapligil (1951), wood anatomy from Richter (1981) and van Rijckevorsel (2002), stomatal morphology from van der Merwe and van Wyk (1994), cuticle from Christophel et al. (1996) and Nishida and van der Werff (2011), floral morphology and anatomy from Sastri (1953, 1965), androecial development from Buzgo et al. (2007), some embryological details from Sastri (1958b), Heo et al. (1998) and Endress and Sampson (1983), fruit anatomy from Heo (199-), cytology from Oginuma et al. (1998), and chromosome size from de Moraes et al. (2007).
Phylogeny. Hypodaphnis, with an inferior ovary, is sister to the rest of the family, then Cassytha (but a long branch), then [Beilschmeidia + Cryptocarya + Endiandra], then Caryodaphnopsis, then [Chlorocardium + Mezilaurus + Williamodendron], then the rest of Lauraceae (Rohwer 2000: matK); for more details, see Chanderbali et al. (2001). There are a number of taxa with long branches, and complex analyses by Rohwer and Rudolph (2005) strongly suggest a slight modification of these relationships: [Hypodaphnis [[the Cryptocarya group] [Cassytha [[Caryodaphnopsis + Neocinnamomum] [[the Mezilaurus group] [The Rest]]]]]] - most of these clades have about 100% posterior probabilities. If this topology is confirmed, it will have considerable implications for character evolution (see above). Although Han et al. (2014) obtained a topology in which Hypodaphnis was embedded in a clade largely made up of clades two and four above, this may be a rooting problem. Massoni et al. (2014) found a clade including Hypodaphnis, Cassytha and Eusideroxylon to be sister to the rest of the family, but these relationships were weakly supported, while L. Li et al. (2016) found that Caryodaphnopsis and Neocinnamomum were on either side of Cassytha, and although support was quite strong, sampling could have been denser. Cassytha weakly linked with Cryptocarya, Endiandra, etc., [Caryodaphnopsis + Neocinnamomum] were the next clade from the base, but support for the position of Cassytha was weak (Z.-D. Chen et al. 2016).
Relationships are beginning to be resolved within the Cryptocarya clade (Rohwer et al. 2014). Litsea is polyphyletic, although section Litsea is monophyletic, and Lindera is also polyphyletic (Fijridiyanto & Murakami 2009). The recognition of Neolitsea appears to make Actinodaphne paraphyletic (Li et al. 2007, esp. 2008). For relationships in the Persea area, see Rohwer et al. (2009); Phoebe and Persea are para/polyphyletic. Cinnamomum is paraphyletic, although only a moderate amount of synonymization would make it monophyletic; there are three main clades, one made up largely of section Camphora that is sister to the other two which are largely made up of section Cinnamomum (J.-F. Huang et al. 2015). For relationships in the Nectandra (paraphyletic)/Ocotea (polyphyletic) area, see Trofimov et al. (2016).
Classification. The classical genera are very difficult to recognise without flowers and are rather unsatisfactory even with them. They are often based on single character differences in the androecium, such as sporangium number and direction of sporangium opening. Both extrorse and introrse anthers can occur in the same flower, thecae may be 2 or 4, their arrangement on the connective varies, etc. (e.g. Kopp 1966; Rohwer et al. 1991; Rohwer 1993, 1994a; van der Werff & Richter 1997); substantial changes in generic limits are to be expected.