EXTANT SEED PLANTS

Plant woody, evergreen; nicotinic acid metabolised to trigonelline; primary cell walls rich in xyloglucans and/or glucomannans, 25-30% pectin [Type I walls]; lignins rich in guaiacyl units; true roots present, xylem exarch; shoot apical meristem complex; arbuscular mycorrhizae +; stem with ectophloic eustele, endodermis 0, xylem endarch; vascular tissue in t.s. discontinuous by interfascicular regions; vascular cambium + [xylem ("wood") differentiating internally, phloem externally]; wood homoxylous, tracheids +; tracheid/tracheid pits circular, bordered; sieve tube/cell plastids with starch grains; phloem fibers +; stem cork cambium superficial, root cork cambium deep seated; nodes ?; leaf vascular bundles collateral; leaves spiral, simple, axillary buds?, prophylls [including bracteoles] two, lateral; plant heterosporous, sporangia eusporangiate, on sporophylls, sporophylls aggregated in indeterminate cones/strobili; true pollen [microspores] +, mono[ana]sulcate, pollen exine and intine homogeneous, ovules unitegmic, crassinucellate, megaspore tetrad tetrahedral, only one megaspore develops, megasporangium indehiscent; male gametophyte development endo/exosporic, gametes two, with cell walls; female gametophyte endosporic, initially syncytial, walls then surrounding individual nuclei; seeds "large", first cell wall of zygote transverse, embryo straight, endoscopic [suspensor +], short-minute, with morphological dormancy, white, cotyledons 2; plastid transmission maternal; two copies of LEAFY gene, PHY gene duplication, mitochondrial nad1 intron 2 and coxIIi3 intron present.

MAGNOLIOPHYTA

Plant woody, evergreen; lignans, O-methyl flavonols, dihydroflavonols, triterpenoid oleanane, non-hydrolysable tannins, quercetin and/or kaempferol +, apigenin and/or luteolin scattered, cyanogenesis via tyrosine pathway, lignins derived from both coniferyl and sinapyl alcohols, containing syringaldehyde [in positive Maüle reaction, syringyl:guaiacyl ratio less than 2-2.5:1], and hemicelluloses as xyloglucans; root apical meristem intermediate-open; root vascular tissue oligarch [di- to pentarch], lateral roots arise opposite or immediately to the side of [when diarch] xylem poles; origin of epidermis with no clear pattern [probably from inner layer of root cap], trichoblasts [differentiated root hair-forming cells] 0; stem with 2-layered tunica-corpus construction; wood fibers and wood parenchyma +; reaction wood ?, with gelatinous fibres; starch grains simple; primary cell wall mostly with pectic polysaccharides; tracheids +; sieve tubes eunucleate, with sieve plate, companion cells from same mother cell that gave rise to the tube, the sieve tube with P-proteins; nodes unilacunar; stomata with ends of guard cells level with aperture, paracytic; leaves with petiole and lamina [the latter formed from the primordial leaf apex], development of venation acropetal, 2ndary veins pinnate, fine venation reticulate, vein endings free; flowers perfect, polysymmetric, parts spiral [esp. the A], free, numbers unstable, P not differentiated, outer members not enclosing the rest of the bud, A many, development centripetal, with a single trace, introrse, filaments stout, anther ± embedded in the filament, tetrasporangiate, dithecal, with at least outer secondary parietal cells dividing, each theca dehiscing longitudinally by action of hypodermal endothecium, endothecial cells elongated at right angles to long axis of anther, tapetum glandular, binucleate, microspore mother cells in a block, microsporogenesis successive, pollen subspherical, binucleate at dispersal, trinucleate eventually, tectum continuous, endexine compact, lamellate only in the apertural regions, pollen tube elongated, with callose plugs, penetrating between cells, growth rate moderate, siphonogamy occuring, nectary 0, G free, several, ascidiate, with postgenital occlusion by secretion, few [?1] ovules/carpel, ovules marginal, anatropous, bitegmic, micropyle endostomal, integuments 2-3 cells thick, megasporocyte single, megaspore lacking sporopollenin and cuticle, chalazal, female gametophyte ?type, stylulus short, stigma ± decurrent, wet [secretory]; P deciduous in fruit; seed exotestal; double fertilisation +, endosperm ?diploid, cellular [first division oblique, micropylar end initially with a single large cell, chalazal end more actively dividing], copious, oily and/or proteinaceous, embryo cellular ab initio; germination hypogeal, seedlings/young plants sympodial; Arabidopsis-type telomeres [(TTTAGGG)_n]; whole genome duplication, single copy of LEAFY and RPB2 gene, knox genes extensively duplicated [A1-A4], AP1/FUL gene, paleo AP3 and PI genes [paralogous B-class genes] +, with "DEAER" motif, SEP3/LOFSEP and PHYA/PHYC gene pairs.

Possible apomorphies are in bold. Note that the actual level to which many of these features, particularly the more cryptic ones, should be assigned is unclear, because some taxa basal to the [magnoliid + monocot + eudicot] group have been surprisingly little studied. Furthermore, details of relationships among gymnosperms will affect the level at which some of these characters are pegged.

NYMPHAEALES [AUSTROBAILEYALES [[CHLORANTHALES + MAGNOLIIDS] [MONOCOTS [CERATOPHYLLALES + EUDICOTS]]]]: vessels +, elements with scalariform perforation plates; pollen tectate-columellate, tectum reticulate [perforated]; nucleus of egg cell sister to one of the polar nuclei; ?genome duplication; "DEAER" motif in AP3 and PI genes lost, gaps in these genes.

PIPERALES Dumortier  Main Tree, Synapomorphies.

Herbs; sesquiterpenes [e.g. gamma-elemene] +; vessel elements with simple perforations; starch grains compound; primary stem with distinct bundles; vessel elements in radial files, with simple perforations; wood with broad rays; nodes often swollen; stomata not paracytic; leaves 2-ranked, 2ndary veins palmate, (stipules intrapetiolar); A in 3's, G occlusion?; seed ± tegmic, endotegmen tanniniferous; PHYE gene absent. - 4 families, 17 genera, 4090 species.

There are a number of reports of delayed fertilisation in Piperales, including in some Piperaceae (Sogo & Tobe 2006d for references).

Carlquist et al. (1995) suggest a number of wood anatomical characters that may be common to this clade, thus wood in both some Aristolochiaceae and Piperaceae is storied (Carlquist 1992). There is considerable variation in the differentiation of the embryo in the Piperaceae, and the polarity of evolution of this feature is unclear, as is that of micropylar morphology, etc.

Relationships around Aristolochiaceae are unclear, although the pairing [Piperaceae + Saururaceae] is often strongly supported (e.g. Neinhuis et al. 2001, Nickrent et al. 2001). Hilu et al. (2003: matK analysis alone) even suggest Aristolochiaceae are paraphyletic and include the rest of the order (Hydnoraceae were not sampled). Neinhuis et al. (2000) suggested that Lactoridaceae were not to be included in Aristolochiaceae, although subsequent analyses have tended in the opposite direction (e.g. Neinhuis et al. 2005: weak support for inclusion of Lactoridaceae in Aristolochiaceae as sister to Aristolochioideae). Similar relationships were found by Davis et al. (2004: support rather weak - ±70%, Hydnoraceae not included). In the two-gene analysis of Wanke et al. (2007: Hydnoraceae again not included) support for Lactoridaceae as sister to Aristolochioideae was quite strong (82% bootstrap: see also Borsch et al. 2005; Qiu et al. 2005), however, the position of Asaroideae was uncertain; it might be sister to [Lactoridaceae + Aristolochioideae] or to [Piperaceae + Saururaceae]! Relationships of the parasitic Hydnoraceae are still unclear, although they go in this general area (e.g. barkman et al. 2007); Nickrent and Blarer (2005) found moderate support for the clade [Hydnoraceae + Aristolochioideae].

Takhtajan (1997) placed Aristolochiales in Magnolianae, his Lactoridanae were monotypic. In some floral details, Saururaceae are very like Acoraceae (Buzgo & Endress 2000), e.g. they both have monosymmetric flowers, but these probably represent convergences. Similarly, the three-merous perianth and adaxial prophylls that seem to suggest a relationship between Piperales and monocots (and Nymphaeales), the now unlikely paleoherb hypothesis (for which see e.g. Donoghue & Doyle 1987), also represent parallelisms.

For floral development, see Tucker and Douglas (1996).

Includes Aristolochiaceae, Hydnoraceae, Piperaceae, Saururaceae.

Synonymy: Aristolochiales Dumortier, Asarales Horaninow, Hydnorales Reveal, Lactoridales Reveal - Aristolochianae Doweld, Lactoridanae Reveal & Doweld, Piperanae Reveal - Piperidae Reveal - Aristolochiopsida Bartling, Asaropsida Horaninov, Piperopsida Bartling

Hydnoraceae + Aristolochiaceae: P connate, valvate, A extrorse, embryo undifferentiated.

Although these taxa may form a clade, relationships between them are unclear (Nickrent et al. 2002).

HYDNORACEAE C. Agardh   Back to Piperales

Echlorophyllous root parasites; starch grains?; sieve tube plastids without starch or protein inclusions; stomata?, cuticle wax crystalloids 0; leaves 0; flowers arising endogenously from roots, 3-4(-5)-merous, large, P uniseriate, thick and fleshy, A = adnate to and opposite P, sessile, connate, polythecate, pollen variously sulcate or trichotomocolpate, ektexine homogeneous, (staminodes alternating with P, below A), G inferior, alternating with P, placentation of parietal or apical lamellae, many atropous unitegmic tenuinucellate ovules/carpel, nucellar epidermis persistent, embryo sac bi- or tetrasporic, nucellar cap?, style 0, stigma broad, cushion-shaped; fruit baccate, ± circumscissile or not; exotestal cells with thickened inner walls (not); endosperm cells with thick walls, arabinose and starch +, perisperm thin; n = ?; germination via germ tube.

2[list]/7. Arabian Peninsula, Africa, Madagascar; Costa Rica and S. South America (Map: from the Parasitic Plants Website 2004). [Photo - Prosopanche Staminate Flower © L. Musselman, Flower © R. Polhill & Paolo, Fruit © G. Williams.]

• Hydnoraceae are leafless and echlorophyllous root parasites that can be recognised by their large flowers with a single, thick, basally connate, valvate perianth whorl that is brownish and cracked outside and coloured inside, stamens opposite the perianth lobes, and inferior ovary; the fruit contains many small seeds, some 90,000 or so.

Pollination of the foetid flowers of Hydnora is by flies and beetles, as in Aristolochiaceae (Bolin et al. 2006b). Dispersal is by mammals. Tennakoon et al. (2005, 2007) suggest that the so-called pilot roots, with their scattered vascular bundles, are in fact better interpreted as modified stems. Cork is continuous over the apical meristem. Each flower has up to 35,000 ovules. In Hydnora triceps both flower and fruit are underground.

The connate, valvate perianth, extrorse anthers, successive microsporogenesis, and inferior ovary all suggest a relationship with Aristolochiaceae, although some of the characters are plesiomorphies and ovary position is clearly very labile around here. An association along these lines is suggested by Nickrent and Duff (1996), Blarer et al. (2000) and Nickrent et al. (2001, 2002), while Nickrent and Blarer (2005) suggest that there is a clade [Hydnoraceae + Aristolochioideae]. However, Hydnorales were placed in Rafflesianae by Takhtajan (1997).

Carpel orientation is suggested by stigma position (Baillon 1888); other information is taken from Cocucci (1976: embryology) and Meijer (1993: general), for germination, see Bolin et al. (2006a). See Hegnauer (1966, 1989) for what little is known about chemistry.

ARISTOLOCHIACEAE Jussieu   Back to Piperales

Flavonols +; wood storied; stomata anomocytic; leaves conduplicate, heart-shaped, 2ndary venation palmate, prophyll adaxial; inflorescence cymose: P 3, odd member adaxial, A in 3's, ± sessile, connective extended apically, nucellar cap +, micropyle endostomal, carpels basically free; fruit a follicle; exotestal cells enlarged and thickened or not, endotesta palisade, usu. crystalliferous, exotegmen and layer underneath crossing fibers, (exotegmen radially elongated), endotegmen with reticulate thickenings; endosperm oily.

5-8[list]/480. World-wide, not Arctic (Map: from Poncy 1978; Fl. N. Am. III 1997; de Groot et al. 2006 - S. America?, Australia approximate) - three groups below.

These characters yet to be assigned to their appropriate hierarchical level: hairs uniseriate; petiole with a ring of (three) bundles or incurved U-shaped; cuticle waxes as annular rodlets, palmitone the main wax; P connate, nectaries or secretory hairs on tube, A 5-12, ± connate, usu. initiated in petal?-opposed pairs, (filaments slender), connective prolonged or not, tapetal cells multinucleate, pollen ektexine semitectate-reticulate, granular(-columellate), style short, hollow, stigma dry or wet;

1. Asaroideae O. C. Schmidt

Growth sympodial; sieve tube plastids with cuneate protein crystalloids and a large polygonal crystal; (nodes with two traces from central gap - Saruma); inflorescences/flowers terminal; hypanthium +, K and C distinct, pollen sulcate (indistinctly 3-porate), G 9, adnate to hypanthium, otherwise free, (micropyle bistomic) [Saruma], or tube from outer P whorl, inner whorl at most minute [Asarum], stigma with multicellular papillae; K persistent, (fruit an irregularly dehiscent capsule - Asarum); elaiosome extending along the raphe; n = 6, 12, 13, 18, 20, 26.

2/75. N. Temperate, esp. East Asia. [Photos: Saruma Flower, Asarum Flower.]

See Leins and Erbar (1995) for the flowers of Saruma, and Kelly (1998) for relationships in Asarum.

Synonymy: Asaraceae Ventenat

Lactoris + Aristolochioideae: ?

2. Lactoris

?Chemistry; ?cork; rays 0 [internodal regions]; sieve tube plastids with starch grains; nodes 1:2; petiole?; plant glabrous; cuticle waxes as parallel platelets; leaves elliptic, 2ndary veins subpinnate, stipule sheathing, intrapetiolar, adnate to the petiole; plants polygamo-dioecious, inflorescence thyrsoid, bracteoles 0; flowers small, A 6, (inner or both whorls staminodial), pollen in tetrads, saccate, ektexine granular (subcolumellate), G 3, alternating with P, 4-8 pendulous epitropous ?tenuinucellate ovules/carpel, funicle long, endothelium +; coat cells collapsed, two cuticular layers persisting; endosperm with chalazal haustorium; n = 20.

1[list]/1: Lactoris fernandeziana. Chile, the Juan Fernandez Islands. [Photo: Specimen.]

González and Rudall (2001) show that the stipule is initially paired. The perianth members have but a single trace. Endress (1994c) suggested that the androecium in Lactoris was adnate to the gynoecium, as in other Aristolochiaceae, but at most it is adnate to the stipe of the gynoecium. An illustration in Engler (1888) showed a bistomal micropyle. The endotegmen is tanniniferous.

See Engler (1887: general, anatomy), Carlquist (1964: general, 1990: wood anatomy), Hegnauer (1966, 1989: chemistry), Bouman (1971: ovule), Crawford et al. (1986: chemistry), Metcalfe (1987: vegetative anatomy), Kubitzki (1993: general), Tobe et al. (1993) and González and Rudall (2001) for details.

3. Aristolochioideae

Viny (woody); growth monopodial; benzylisoquinoline alkaloids +; sieve tube plastids with polygonal protein crystalloids plus starch grains or protein fibers (starch grains alone); (odd secondary thickening); groups of silicified cells +; serially arranged axillary buds; hairs hooked; (leaves lobed), base of petiole U- or V-shaped; inflorescences axillary, bracts distinct; (flower resupinate), floral primordia monosymmetric, (flowers monosymmetric, microsporogenesis successive - Aristolochia), A 3-12(-40< - Thottea), (in a single whorl), pollen inaperturate, G [4-6], (Thottea has a single fertile carpel), inferior, apically constricted; fruit septicidal and opening laterally, a schizocarp, or dry-baccate, K not persistent; n = (4-)6-7(8+).

2-5/405. Tropics (temperate), relatively less diverse in Africa (inc. Madagascar), few in N. Australia. [Photos - Flowers, Fruits.]

Although the monophyly of Aristolochia is not in question, it is indeed quite variable. It has been suggested that it could be divided into eight genera (Huber 1993), some of which would be well characterised. Some splitting, perhaps into four genera, seems to be favoured (Neinhuis et al. 2005); Wanke et al. (2006b) note that the four main clades all have synapomorphies. González and Stevenson (2002) provide a phylogenetic analysis of the subfamily and suggest that it be split into four genera; Ohi-Toma et al. (2006) propose dividing it into two.

The shrubby habit is derived. The central leaf trace of the woody Aristolochia arborea (the inside of perianth tube looks as if it has a mushroom on its abaxial side!) appears to have three parts, but this may well be a single trace broken up by the broad rays. Aristolochia clematitis appears to have lateral prophylls; lobed leaves are known from Aristolochia. Both dry and wet stigmas occur.

• Aristolochiaceae are more or less herbaceous plants (they are quite often vines) that may be recognised by their adaxial prophylls, exstipulate leaves with palmate venation and entire margins, and 3-merous flowers with extrorse stamens. The ovary is usually inferior and the perianth uniseriate and connate. Only Aristolochia has monosymmetric flowers, only Saruma a perianth differentiated into sepals and petals and a largely superior gynoecium of free carpels.

• Lactoris can be recognised by its small, 2-ranked leaves with intrapetiolar stipules; the prophylls are adaxial. The flowers are small and have three imbricate perianth members and three free carpels.

Pollen like that of Lactoris has been found in Late Cretaceous deposits from S.W. Africa (Zavada & Benzon 1987).

Aristolochia is eaten by caterpillars of the magnificent birdwing butterflies, and the association between caterpillars of the Papilionidae-Troidini and Aristolochiaceae (they are apparently absent from Saruma, although larvae of Luehdorfia [Zerynthiini] have been reported from this plant) has been studied in some detail (e.g. Weintraub 1995); there seems to be no particular association between the phylogeny or chemistry of the plant and the butterflies (Silva-Brandão & Solferini 2007). The flowers of some Aristolochiaceae show thermogenesis (Seymour 2001).

Aristolochic acid is closely related biosynthetically to benzylisoquinoline alkaloids (Gershenzon & Mabry 1981). Aristolochia has cuticular wax rodlets, but other genera lack crystalloids. Ding Hou (1984) notes that the leaves wither on the plant and are not abscised. González and Stevenson (2000) suggest that the uniseriate perianth is derived from the outer whorl of a biseriate perianth; in any inner whorl, "petal" bases are narrow, although the bases of members of the outer whorl encircle the axis; there are also suggestions that "petals" may be derived from stamens (see also Leins & Erbar 1995; Ronse De Craene et al. 2003), although their position (petals are found in the angles of the outer whorl, suggesting that it is in fact a complex structure; stamens are more or less adnate to the style) perhaps makes this unlikely. Jaramillo and Kramer (2004) describe the basic perianth condition for the family as being unipartite (= uniseriate), with its ancestors having "multiple" whorls. The median outer tepal is adaxial (González & Stevenson 2000a), i.e. not in the monocot position, in some taxa, although it is abaxial in Aristolochia s. str., but with the exception of A. grandiflora, and Pararistolochia (Neinhuis et al. 2005: ?other taxa). Spichiger et al. (2004) show a floral diagram for Aristolochia where the six stamens and carpels are not opposite to the perianth members - nor would be opposite sepals or petals, if such were present. González and Stevenson (2000b) note that the stigmas of Aristolochia are commissural, and that when there is only a single whorl of stamens in the flower, it is the inner whorl.

See Hegnauer (1964, 1989) for chemistry, Huber (1985) for seed characters and infrafamilial classification, Huber (1993) for general information, González (1999) for inflorescence morphology, González et al. (2001) for microsporogenesis, Behnke (2003) for sieve tube plastids, Kelley and González (2003) for a morphological phylogenetic analysis, Leins et al. (1988) for floral development, González and Rudall (2001) for ovule and seed development, and Mulder (2003) for pollen, which, however, is poorly known. I thank Mauricio Diazgranados for comments.

Piperaceae + Saururaceae: root epidermis from inner layer of cap; stomata tetracytic; cuticle wax crystalloids usu. 0; leaves supervolute, base broad, ± sheathing, (stipules on petiole); inflorescence spicate, often terminal; flowers small, rather obscurely monosymmetric, P 0, filaments rather slender, microsporogenesis simultaneous, pollen grains <20 µm, G with odd member adaxial [when 3], ovules straight [atropous], stigma dry; seed coat exo- and endotegmic; perisperm +, starchy, endosperm ?type, scanty, embryo broad.

Some information is taken from Murty (1960) and Tucker et al. (1993). See Jaramillo et al. (2004) for the complexities of floral evolution in this group; it is possible that a four-carpellate gynoecium is the basic condition.

PIPERACEAE Martynov   Back to Piperales

Also trees or lianes; flavonols, tannins 0; bundles scattered or in 2 rings; rays 8-45-seriate [other Piperales?]; (cork in outer cortex); cambium storied; (vessel elements with scalariform perforations); mucilage canals +; petiole bundles arcuate; prophyll single, basal, adaxial to lateral, with a fairly prominent axillary bud; leaf (supervolute; 2ndary venation pinnate; margins lobed), (stipule +; margins sheathing; ligule); (inflorescence racemose), bracts peltate or clavate; A 1-10, often 2 or 3 + 3, latrorse to extrorse, thecae not dehiscing their entire length, pollen ektexine tectate, G [2-5], 1 basal ovule/carpel, outer integument 5 cells thick, inner to 7 cells thick - Macropiper), micropyle (bi - Piper-Heckeria) endostomal, embryo sac tetrasporic; fruit berry or drupe; seeds with at least transiently developed exo- and endotegmic layers; endosperm (nuclear - some Piper, Zippelia) 3n to highly polyploid; n = 11, 13, 19.

5[list]/3615. Pantropical (Map: from Jaramillo & Manos 2001; Wilson 2007; M. A. Jaramillo, pers. comm.) - three groups below.

1. Verhuellioideae Samain & Wanke

A 2, G 3-4.

1/3. Cuba and Hispaniola.

2. Zippelioideae Samain & Wanke

A 4, 6, G 3-5.

2/6. China to Malesia, Central and South America.

3. Piperoideae Arnott

A 2-6, G 1-4.

2/3600: Piper (2000), Peperomia (1600). Pantropical. Photo: Peperomia - Flower, Piper - Flower, Fruit.]

• Piperaceae may be recognised vegetatively by their herbaceous habit and/or their separate vascular bundles in the stem, their swollen nodes, and their soft and/or fleshy leaves that are often cordate at the base. The minute flowers lack a perianth and are often borne in dense spikes; individual flowers are subtended by peltate to clavate bracts. Some species of Piper look remarkably like Araceae!

Peperomia is a notable component of the epiphytic flora, particularly in the neotropics. Carollia bats (Phyllostomidae) are abundant New World fruit-eating bats that specialize on eating Piper living in the understory; Old World Piper are bird-dispersed (Fleming 2004).

The inflorescence of Zippelia is described as being racemose, the flowers being arranged sympodially (Lei et al. 2002). Syncarpy is weak; Piper has separate carpel primordia. Each carpel has a single ventral bundle. The embryo sac of Peperomia is 16-nucleate, the chalazal nuclei fusing, that of Zippelia is 16-celled, while that of Piper is 8-celled, the antipodals being polyploid. The endosperm of Peperomia may be up to 15n. The embryo at least sometimes lacks a suspensor, but I am not sure of the distribution of this feature, while in Zippelia the zygote remains as such up to the maturity of the seed. In Zippelia the endotegmen alone is persistent.

Relationships may be [Verhuellia [[Zippelia + Manekia] [Piper + Peperomia]]] (Jaramillo & Callejas 2004; Wanke et al. 2006a, 2007a, b); this entails redrawing the old subfamilial boundaries. The recent discovery that Verhuellia is sister to the rest of the family (Wanke et al. 2007b) changes hypotheses as to the plesiomorphous characters of the family; of the three genera in the two small clades that are successively sister to Piper and Peperomia, we know little about two. There is considerable variation - some infraspecific - in the particlar kind of tetrasporic embryo sac development in the family (Arias & Williams 2008: Verhuellia not yet studied). Jaramillo and Callejas (2004) and Smith et al. (2005) found that Piper s. str. was divided into New and Old World clades, the latter being divided into a mainland Asian clade, containing both the two endemic African species and a species from Australia, and also a Pacific islands Macropiper clade including the economically very important Piper methysticum (Jaramillo & Callejas 2004 found that the single African species they examined grouped with their Pacific clade). Interestingly, in a trnK/matK analysis, Wanke et al. (2007a) found much less resolution within Piper than Peperomia. For the classification of Piperaceae followed here, see Samain et al. (2008); the subfamilies do not seem to be easily characterisable.

Peperomia itself is a very distinctive genus. It has scattered vascular bundles, spiral or opposite leaves, usually with narrow insertions on the stem and lacking stipules, the flowers have two bisporangiate/monothecal extrorse stamens, inaperturate pollen, a single carpel with a penicillate stigma, and an unitegmic (the integument is ca 2 cell layers across) tenuinucellate ovule. However, its recognition as a separate family would make Piperaceae paraphyletic. For the phylogeny of Peperomia, see Wanke et al. (2006a, 2007).

Some information is taken from Hegnauer (1969, 1990: chemistry), Weberling (1970: stipules), Burger (1972: Central American Piper), Bornstein (1991: general), Johri et al. (1992: embryology), Tebbs (1993: general), Jaramillo and Manos (2001: phylogeny and morphology of Piper) and Lei et al. (2002: embryology of Zippelia), for floral development, see Lei and Liang (1998: Piper; 1999: Peperomia and Tucker et al. (1993: Zippelia), and for phytoliths, see Piperno (2006). I thanke S. Wanke for estimates of species numbers.

Synonymy: Peperomiaceae A. C. Smith

SAURURACEAE Martynov   Back to Piperales

Plant rhizomatous or stoloniferous; leucanthocyanins +, alkaloids 0; (bundles in two rings - Saururus); vessel elements often with scalariform perforations; petiole bundles arcuate or annular; cuticle waxes as parallel platelets; (leaf ptyxis involute - Anemopsis, Saururus); bract at base of inflorescence large, petaloid (not), (common flower/bract initials); A often 3, or 6 or 8 in two whorls, but variable, ± connate in pairs and/or adnate to the ovary or not, introrse, pollen (trichotomsulcate), ektexine tectate-columellate, G 4, or [3-4], (inferior), placentation often parietal, (1-)2-9(-12) ovules/carpel, micropyle zig-zag; fruit dry, indehiscent or follicle; exo- and endotegmic cells much thickened; (endosperm helobial); n = 9, 11, 12.

5[list]/6. North Temperate. (Map: from Wu 1983; Ying et al. 1993; Fl. N. Am. III 1997 - in Sumatra?, introduced into Java?).[Photos - Collection] [Photo - Saururus Habit © E. Pontieri] [Photo - Saururus Inflorescence © E. Pontieri]

• Saururaceae may be recognised by their often aromatic and rather fleshy leaves with broad bases and palmate venation and by their spicate inflorescences that usually have a large, basal inflorescence bract. The flowers are small, without a perianth, but there are clearly three to four carpels.

Anemopsis, alone in the family, has a relatively well developed vascular cambium and also simple vascular perforations... (Carlquist et al. 1995). According to Murty (1960) the single intrapetiolar stipule represents two, connate stipules. Houttuynia is tenuinucellate. Each carpel has two ventral bundles, whether or not they are fused.

Smith and Stockey (2007) describe a fossil Saururaceae from the middle Eocene; although it differs in stamen number from numbers normally associated with the family, there is clearly much variability here.

Houttuynia and Anemopsis are sister taxa and sister to the rest of the family in a matR analysis (Meng et al. 2002, 2003). The first pair are also found in a three-gene analysis, but the support is poor; Saururus + Gymnotheca are a better-supported pair (Jaramillo et al. 2002). These two pairs of genera are also recovered in other molecular analyses (e.g. Neinhuis et al. 2005), although they are not found in morphological analyses.

Some information is taken from Wood (1971: general), Hegnauer (19673, 1990: chemistry) and Wu and Kubitzki (1993: general); see Carlquist et al. (1995) for wood anatomy.