EXTANT SEED PLANTS

Plant woody, evergreen; nicotinic acid metabolised to trigonelline, (cyanogenesis via tyrosine pathway); primary cell walls rich in xyloglucans and/or glucomannans, 25-30% pectin [Type I walls]; lignins rich in guaiacyl units; true roots present, apex multicellular, xylem exarch, branching endogenous; arbuscular mycorrhizae +; shoot apical meristem multicellular, interface specific plasmodesmatal network; stem with ectophloic eustele, endodermis 0, xylem endarch, branching exogenous; 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 ?; stomata ?; leaf vascular bundles collateral; leaves spiral, simple, axillary buds?, prophylls [including bracteoles] two, lateral, veins -5 mm/mm² [mean for all non-angiosperms 1.8]; plant heterosporous, sporangia eusporangiate, on sporophylls, sporophylls aggregated in indeterminate cones/strobili; true pollen [microspores, i.e. no distal pore for release of gametes] +, grains mono[ana]sulcate, exine and intine homogeneous, ovules unitegmic, crassinucellate, megaspore tetrad tetrahedral, only one megaspore develops, megasporangium indehiscent; male gametophyte development first endo- then exosporic, tube developing from distal end of grain, to ca 2 mm from receptive surface to egg, gametes two, with cell walls, with many flagellae; 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 [N/O//A/C and P//BE lines], 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 in ANITA grade?], 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 a sieve plate and cytoplasm with P-proteins, companion cells from same mother cell that gave rise to the sieve tube; nodes unilacunar [1:?]; stomata with ends of guard cells level with pore, paracytic, outer stomatal ledges producing vestibule; leaves with petiole and lamina [the latter formed from the primordial leaf apex], development of venation acropetal, 2ndary veins pinnate, fine venation reticulate, veins (1.7-)4.1(-5.7) mm/mm², endings free; flowers perfect, polysymmetric, parts spiral [esp. the A], free, development in general centripetal, numbers unstable; P not sharply differentiated, outer members not enclosing the rest of the bud, smaller than inner members; A many, 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, walls developing by centripetal furrowing; pollen subspherical, binucleate at dispersal, trinucleate eventually, tectum continuous or microperforate, ektexine columellar, endexine thin, compact, lamellate only in the apertural regions; nectary 0; G free, several, ascidiate, with postgenital occlusion by secretion, few [?1] ovules/carpel, ovules marginal, anatropous, bitegmic, [outer integument often largely subdermal in origin, inner integument dermal], micropyle endostomal, integuments 2-3 cells thick, megasporocyte single, megaspore lacking sporopollenin and cuticle, chalazal, female gametophyte four-celled [one-modular, nucleus of egg cell sister to one of the polar nuclei], stylulus short, hollow, stigma ± decurrent, dry [not secretory]; P deciduous in fruit; seed exotestal; pollen germinating in less than 3 hours, tube elongated, growing at 80-600 µm/hour, with callose plugs and callose-based walls, penetrating between cells, siphonogamy, penetration of ovules within ca 18 hours, distance to first ovule 1.1.-2.1 mm; 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, minute; 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 + C/PHYB + E gene pairs.

Evolution. Possible apomorphies for flowering plants 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, there is considerable variation between families in particular for several of these characters, and also because details of relationships among gymnosperms will affect the level at which some of these characters are pegged. For example, if reticulate-perforate pollen is optimized to the next node on the tree (see Friis et al. 2009 for a discussion), it effectively makes the pollen morphology of the common ancestor of all angiosperms ambiguous....

NYMPHAEALES [AUSTROBAILEYALES [[CHLORANTHALES + MAGNOLIIDS] [MONOCOTS [CERATOPHYLLALES + EUDICOTS]]]]: vessels +, elements with scalariform perforation plates, axial parenchyma diffuse or diffuse-in-aggregate; tectum reticulate-perforate [here?]; ?genome duplication; "DEAER" motif in AP3 and PI genes lost, gaps in these genes.

COMMELINIDS   Back to Main Tree

Unlignified cells walls with UV-fluorescent ferulic and coumaric acids; (vessels in stem and leaves); SiO₂ bodies in leaves; stomata para- or tetracytic, (cuticular waxes as aggregated rodlets [looking like a scallop of butter]); inflorescence bracteate; (P fully bicyclic [= K + C, stamens adnate to corolla/inner P]), pollen starchy; embryo short, broad.

Evolution. The stem group of commelinids is dated to ca 122 million years before present, divergence within it begins ca 120 million years before present (Janssen & Bremer 2004) - or the figures are 107-98, 99-91 (Arecaceae sister to rest) and 94-86 million years before present respectively (Dasypogonaceae sister to remainder: Wikström et al. 2001), or ca 116 million years before present, Arecaceae and Dasypogonaceae diverging almost immediately, and Poales and [Commelinales = Zingiberales] within 4 million years (Bremer 2000b).

Larval food plants of the butterflies Nymphalidae-Morphinae and Satyrinae are widely distributed in this group (Ehrlich & Raven 1964), as are those of the beetles Chrysomelidae-Hispinae+Cassidinae (Jolivet 1988; Schmitt 1988; Vencl & Morton 1999; Chaboo 2007). Indeed, these latter are also found in some other monocots, but 14/39 tribes for which there is at least some host plant data for their larvae are found on commelinids, 26/39 on some monocot or other (Chaboo 2007). The beetle larvae eat between the veins. Larvae are also found on Boraginaceae, Solanaceae, Convolvulaceae and Asteraceae, in particular, among the core eudicots - asterids seem to be particularly favoured. However, it is unclear if Criocerinae are in a clade immediately related to Hispinae and related monocot-eating beetles, or not (check Chaboo 2007; cf. Wilf et al. 2000 and Gómez-Zurita et al. 2007).

The rate of molecular evolution in commelinids is generally high, ca 0.003 substitutions/site/million years (Smith & Donoghue 2008). However, for some genes like ndhF, at least, the rate of molecular evolution is similar in Asparagales, etc. (Givnish et al. 2006). On the other hand, although genes in all three genomic compartments apparently evolve slowly in Arecaceae (Wilson et al. 1990; Baker et al. 2000a, 2000b), the rate seems not that much less than in a number of other monocots, especially monocots other than commelinids (S. W. Graham et al. 2006); was there an increase in the rate of molecular change within some commelinids, some Poales being spectacular examples?

Chemistry, Morphology, etc. Silicon concentrations in tissues are generally high, although not of course in groups that do not have SiO₂ bodies, although even there they are not always high (Ma & Takahashi 2002). Lignins from Poaceae and Arecaceae (and elsewhere?) have p-coumaryl alcohol as well as coniferyl and sinapyl monomers (Seigler 1998). For the chemistry of the distinctive epicuticular waxes scattered in this area of the monocots (Barthlott & Fröhlich 1983), see Meusel et al. (1994). Although vessels in the stem and leaves are common (Wagner 1977), it may well be incorrect to treat this as a synapomorphy. In those few commelinids whose floral development has been studied in detail, expression of the B-class gene orthogue of PISTILLATA seems to be restricted to the stamens/staminode and petals (Adam et al. 2007); this may be connected with the fully bicyclic nature of the perianth found in many members of this clade. In some of the few other monocots studied, development may be somewhat different. Starch-containing pollen is common, but has not been found in Hanguanaceae or Dasypogonaceae (only one species of the latter examined) and in some species of Haemodoraceae, Bromeliaceae, etc. Broad embryos may be a synapomorphy at about this level.

Some morphological information about the commelinids is summarized by Givnish et al. (1999).

Phylogeny. Commelinids are well supported in molecular studies (e.g. S. W. Graham et al. 2006, and references), and they have morphological support as well, but relationships between the main groups within them are unclear. Hilu et al. (2003: matK) suggested that Poales may be sister to other commelinids, but the posterior probabilities are low. Neyland (2002b: 26s rDNA) found that Dasypogonaceae were strongly associated with Restionaceae and other families (Poales), but this particular relationship is not suggested by other molecular data, nor does it appear in morphological analyses. However, recent work using multi-gene data sets is not linking Dasypogonaceae with Arecales, even if where they end up has no strong support (see Givnish et al. 2006 and Chase et al. 2006 - near Poales; S. W. Graham et al. 2006 - near [Commelinales + Zingiberales]). [Commelinales + Zingiberales] may be a nore or less well supported group (Chase et al. 2006; Givnish et al. 2006; Soltis et al. 2007a). Arecales sometimes appear as sister to Poales (e.g. S. W. Graham et al. 2006), but with very weak support, or support for groupings of major clades may in general be weak (Chase et al. 2000a; Soltis et al. 2007a). See also Commelinales, Zingiberales, and Poales for further discussion of relationships. Changes in relationships may well occur, and so the topology in this part of the tree is only tentative.

Classification. Givnish et al. (1999) erected a classification of four superorders and 10 orders for the commelinids based on a rbcL phylogeny, A.P.G. (1999, 2003) has recognised many fewer orders. These are generally well supported clades with stable contents.

Unplaced:  Back to Main Tree

DASYPOGONACEAE Dumortier

Plant non-mycorrhizal; rhizomatous or arborescent, (extensive primary thickening +); vessels only in roots; 2 peripheral phloem strands in foliar bundles; leaves spiral, (serrulate), sheath well developed, bases persisting; P dry, septal nectaries +, 1 ascending epitropous[?] ovule/carpel, micropyle bistomal; seeds rounded, testa pale yellow; endosperm type?.

4[list]/16. West Australia, Victoria. [Photo - Habit, Flowers].

Dasypogon + Calectasia

Hairs branched; (chelidonic acid + - Dasypogon); raphides only in flowers; SiO₂ epidermal; stomatal accessory cell ontogeny odd; leaf bundle girders 0; inflorescence capitate, flowers in clusters or single; T, or outer whorl only, connate, floral tube short; A adnate to base of T, (anthers porose - Calectasia); fruit indehiscent; tegmen collapsing, massive storage nucellus [below embryo sac]; n = 7, 9; cotyledon not photosynthetic, mesocotyl and coleoptile +.

2/14. S.W. Australia, Victoria (map: from Barrett & Dixon 2001; FloraBase 2004).

Synonymy: Calectasiaceae Endlicher

Kingia + Baxteria

Raphides 0; leaf bundle girders + [originating in mesophyll]; inflorescence capitate or single-flowered [Baxteria], surrounded by bracts, stalk bracteate; T (large - Baxteria) free; A ± adnate to base, pollen extended sulcate-unipantocolpate; fruit indehiscent or explosively septifragal [Baxteria]; storage nucellus?; n = 7; seedling?

2/2. S.W. Australia (map: from FloraBase 2004).

Synonymy: Baxteriaceae Takhtajan, Kingiaceae Endlicher

Evolution. Stem group Dasypogonaceae are dated to ca 119 million years before present, divergence within crown group Dasypogonaceae to ca 100 million years before present (Janssen & Bremer 2004: they place Dasypogonaceae rather near the base of the commelinids). Dasypogon and Calectasia may have diverged 49-41 million years before present (Wikström et al. 2001).

Chemistry, Morphology, etc. Calectasia has a 1-locular ovary; some species have stilt roots. For Calectasia, see Barrett and Dixon (2001). In Kingia the apical meristem is depressed, as in Arecaceae, and the plant is also monopodial; adventitious roots grow down to the ground in persistent sheathing leaf bases.

Information is taken from Chanda and Ghosh (1976: pollen), Rudall and Chase (1996) and Clifford et al. (1998b).

Previous Relationships. Dasypogonaceae have often been linked with other similar-appearing xeromorphic monocots from Australia such as Xanthorrhoeaceae and Laxmanniaceae (previously Lomandraceae), as in Takhtajan (1997); the two latter families are in Asparagales.

Synonymy: Dasypogonales Reveal

ARECALES Bromhead  Main Tree, Synapomorphies.

Plant woody, monopodial; vessels also in stem and leaf; cuticular waxes as aggregated rodlets, stomata tetracytic; leaves spiral, petiolate, reduplicate-plicate, pinnately pseudocompound or deeply divided; flowers ± sessile, septal nectaries +, 1 apotropous ovule/carpel.

1 family, 189 genera, 2361 species.

Evolution. The rate of molecular evolution in Arecaceae is rather low, as might be expected from a woody plant with a relatively long generation time, and is ca 0.0014 substitutions/site/million years; this is interpreted as representing a reduction in the rate of molecular evolution (Smith & Donoghue 2008; see Gaut et al. 1996 for a comparison between Poaceae and Arecaceae). Seed size in Arecaceae seems to have undergone a notable increase, probably associated with the adoption of the tree habit by the clade (Moles et al. 2005a).

ARECACEAE Schultz-Schultzenstein, nom. cons.//Palmae Jussieu, nom. cons. et nom. alt.   Back to Arecales

Stem unbranched; flavonoid sulphates abundant; fibre bundles both free is mesophyll and attached to epidermes, sheaths of transverse veins fibrous, SiO₂ bodies sometimes hat-shaped, often spiny-verrucate, esp. associated with fibers strands or vascular bundles, epidermal cells rectangular, hypodermal cells rectangular, longitudinally elongate; leaf with closed sheath; plant often monoecious; inflorescences with bicarinate prophyll, on branches prophylls lateral [hence ultimate units are cincinni]; micropylar embryo sac haustorium +; fruit a (dry) berry or drupe; seed 1(-3), rounded; micropylar endosperm haustorium +, endosperm with hemicellulose; cotyledon not photosynthetic, collar short (with roots), primary root strong, branched.

189[list]/2361 - five groups below. Humid tropics and subtropics (warm temperate), Africa is relatively depauperate. [Photo - Flowers, Fruits.]

1. Calamoideae Beilschmied

anticlinal epidermal walls sinuous, adaxial subepidermal fibres +, veins bridging to epidermis via verically-elongated sclereids, SiO₂ bodies ± spherical; internodes usu. well-developed; (leaves palmate); (inflorescence axes adnate to the internode above); breeding system various, flowers in diads; C valvate, (pollen equatorially disulcate - Calameae), ovule basal, epitropous, [funicle twisted], style branched; G covered by reflexed scales, endocarp thin (thick - Eugeissonia); seeds 1-3, sarcotesta usually thick; n = 13, 14.

21/: Calamus (400), Daemonorops (115). Tropical, but esp. Sri Lanka to West Samoa and Fiji (map: from Uhl & Dransfield 1987).

Synonymy: Calamaceae Perleb, Lepidocaryaceae O. F. Cook

Nypoideae [Coryphoideae + Ceroxyloideae + Arecoideae]: anticlinal epidermal walls ± straight, adaxial subepidermal fibres 0.

2. Nypoideae Griffith

Stem dichotomously branched; veins bridging to epidermis via verically-elongated sclereids, sheaths of transverse veins sclereidal, veins sinuous, irregular, epidermal cells hexagonal to spindle-shaped, hypodermal cells hexagonal, transversely elongate; inflorescence axes adnate to the internode above, with staminate spike and carpellate heads; staminate flowers: P undifferentiated; A 3, opposite outer P, connate, extrorse, pollen zonasulcate, pistillode 0; carpellate flowers: staminode 0; G 3 (4), margins conduplicate, ovule [position?], outer integument 10 cells across, placentation laminar to submarginal; n = ?17.

1/1: Nypa fruticans. Malesia (Bengal to Queensland) (map: current distribution in red, from Uhl & Dransfield 1987; fossil records from other places outside this area in blue, from Plaziat et al. 2001).

Synonymy: Nypaceae Le Maout & Decaisne

Coryphoideae + Ceroxyloideae + Arecoideae: (veins bridging to epidermis by fibres); microsporogenesis simultaneous.

3. Coryphoideae Burnett

(Stem branched - e.g. Caryota); no fibre bundles free in mesophyll, (SiO₂ bodies ± spherical); leaves palmate or costapalmate (pinnate), induplicate; inflorescence various, (terminal; adnate to the internode above; plant monoecious - Caryotinae; flowers in triads); C often valvate, microsporocyte with callose ring [not Caryota, Bismarckia], G free, or connate by style, or style present, with 3 [Coryphinae] or 1 [Sabalinae] stylar canals, or style 0 [Caryoteae].

45/ : Coccothrinax (50). Pan tropical (to warm temperate), fewer in South America (map: from Uhl & Dransfield 1987).

Synonymy: Borassaceae Schultz-Schultzenstein, Coryphaceae Schultz-Schultzenstein, Phoeniciaceae Burnett, Sabalaceae Schultz-Schultzenstein

[Ceroxyloideae + Arecoideae]: sheaths of transverse veins sclereidal, veins sinuous, irregular, epidermal cells hexagonal to spindle-shaped.

4. Ceroxyloideae Drude

SiO₂ bodies ± spherical; flowers solitary along the rhachis, (K and C elongate); (seeds more than 3).

8/42. Mostly Central and W. South America, also N.E. Australia, Madagascar, Florida and the Antilles (map: from Uhl & Dransfield 1987).

Synonymy: Phytelephaceae Perleb

5. Arecoideae Burnett

Hypodermal cells hexagonal, transversely elongate; inflorescence with prophyll and bract(s); plant usually monoecious with flowers in triads [central flower carpellate, lateral flowers staminate] or dioecious with flowers in monopodial inflorescences; (1 G fertile), styles + (style +, short or long); n = 16.

112/ : Bactris (240), Dypsis (140), Pinanga (120), Chamaedorea (110), Geonoma (75), Desmoncus (65<), Areca (60), Astrocaryum (50). Pantropical, the most diverse subfamily in South America (map: from Uhl & Dransfield 1987).

Synonymy: Acristaceae O. F. Cook, Ceroxylaceae O. F. Cook, Chamaedoraceae O. F. Cook, Cocosaceae Schultz-Schultzenstein, Geonomataceae O. F. Cook, Iriarteaceae O. F. Cook & Doyle, Malortieaceae O. F. Cook, Manicariaceae O. F. Cook, Pseudophoeniciaceae O. F. Cook, Synechanthaceae O. F. Cook

• Arecaceae can be recognised by their woody stems, large, tough, petiolate leaves with plicate and often apparently compound blades, axillary inflorescences (but Corypha, etc.!) with numerous flowers, and 1-seeded fruits. Cyclanthaceae can be similar vegetatively, but their petioles are usually less woody and the leaf never has a hastula, an adaxial flap-like structure at the apex of the petiole.

Evolution. Stem group Arecaceae are dated to ca 120 million years before present, divergence within the crown group to ca 110 million years before present (Janssen & Bremer 2004), or the dates are 99-91 and 73-63 million years before present respectively (Wikström et al. 2001).

Palm pollen and/or wood is quite common and widely distributed in the later Cretaceous when global temperatures were warmer (Burnham & Johnson 2004). Certainly, present-day palms are very susceptible to frost, most having only a single vegetative meristem yet being unable to produce replacement meristems if the first is killed. Their diversity and diversification in the New World, at least, has been linked to the persistence of the relatively warm and wet areas that they favour (Svenning et al. 2008). Despite the size of the plant and the size of the fruits, dispersal rather than vicariance is increasingly frequently being invoked to explain apects of the present distribution of the family. Distinctive Nypa fossils are known from the early Tertiary when the genus seems to have had a distribution that was more or less world-wide; fossils are known from Tasmania, England (the London Clay flora), etc. (Plaziat et al. 2001 - see map above. For the evolution of the mangrove habitat, see Rhizophoraceae; Nypa prefers less saline conditions than many other mangrove plants, and is found along rivers up to the limit of tidal influences). The scattered and apparently ancient Gondwanan distribution of Ceroxyloideae is probably best explained by several mid-Tertiary trans-oceanic dispersal events (Trénel et al. 2007), while species of Hyophorbe (Arecoideae-Chamaedoreeae) are disjunct on the Mascarenes, and the genus may have radiated there on islands that are now submerged, hopping from island to island (Cuenca et al. 2007); some Myrtaceae, Begoniaceae, and Sapotaceae may show similar island-hopping behaviour. Roncal et al. (2008) explored the biogeography of Antillean palms.

Riodininae-Riodininae butterfly larvae may be found on Arecaceae, along with larvae of the beetle Hispinae-Cassidinae; these latter can be serious pests of oil palms and other commercial or ornamental palms (Chaboo 2007). Pollination is predominantly by insects, whether beetles (mainly Nitidulae and Cuculionidae-Derelomini), flies, which may visit especially understorey palms, and bees (Henderson 1986). Dufaÿ et al. (2003) found that it was volatiles produced by the leaves of Chamaerops humilis that attracted its weevil pollinator. Thermogenesis has been detected in the flowers of some Arecaceae (Seymour 2001). The speciose New World Chamaedoreeae (Arecoideae) are characterised by raphides in the flowers and in Chamaedorea these are particularly common in the perianth and gynoecium; there are other potentially protective structures in the flowers (Askgaard et al. 2008). The family is another example of the eco-morphological combination of shaded conditions, net-veined leaves and fleshy fruits that has evolved several times in monocots (Givnish et al. 2005, 2006b).

In general, seedling morphology is very variable within Arecaceae (Henderson 2006; Tillich 2007). It is particularly notable that in palms with aerial stems there is usually a period of establishment growth as seedlings. During this time the apical meristem becomes gradually larger, and only when it has reached adult size does elongation growth of the trunk occur. With some exceptions, the size of the apical meristem and hence the width of the trunk it produces remains constant for rest of the life of the palm. Iriarteeae (Arecoideae) are an exception to this pattern. There the apical meristem in the above-ground stem becomes gradually larger, and so the trunk becomes gradually stouter; however, massive prop roots from the lower part of the trunk stabilise the otherwise highly unstable structure, and in the older plant the base of the stem rots away, the plant then being supported entirely by the stilt roots.

Arecaceae have the oldest functioning xylem elements and sieve tubes in seed plants. Since the oldest palm is hundreds of years old and there is no secondary thickening, the vascular tissue at the base of the stem mus remain active for the whole life of the plant (note that it has recently been suggested that at least some palms have monocot-type secondary thickening - Angyalossy et al. 2008). Parthasarathy (1974) described phloem development while Tomlinson (2006b) discussed xylem function in the context of the length of the stem (Calamoideae were the focus), although the age of the stem did not shape the discussion. Tomlinson et al. (2009) have recently found that tissues in both stem and root may remain undifferentiated for some time and undergo limited mitosis; their ability to remain metabolically active may help explain the functional longevity of palm vascular tissue. However, the longevity of seed plant cells in general would repay investigation - some xylem parenchyma cells in broad leaved angiosperms may also remain metabolically active for 200 years or so (Spicer & Holbrook 2007).

"Leaflets" of induplicate leaves are V-shaped in cross section, those of reduplicate leaves are inverted V-shaped. "Leaflets" of induplicate leaves are V-shaped in cross section, those of reduplicate leaves are inverted V-shaped. Despite appearances, the leaves of all palms are simple. The deep lobes in simple palm leaves, and the leaflets in apparently compound leaves, are the result of cell death. More particularly, what goes on is rather like abscission, although nothing (apart, sometimes, from the leaf margin) falls off. The parts that will separate first become thin, then split apart; tissue at the zone of separation may protect the rest of the blade as it becomes lignified or suberised, or a cuticle may form. Details of this process may differ even between closely-related species depending on the timing of events (Nowak et al. 2007, 2008). In a number of palms thin "reins" can be found hanging down from the sides of the leaves; these represent the leaf margins of the originally simple leaf. Fibrous filaments between the leaflets is other evidence for cell death. Fibers found at the bases of the leaves are produced by the decay of the sheaths, while the spines found on so many palms are produced in various ways: modified leaflets (Phoenix), adventitious roots (Crysophila, but relatively common), partly detaching outer parts of the stem, again, caused by cell death, etc. Most Calamoideae (the rattans) and some Arecoideae (Desmoncos), are climbers, either by the aid of of a long, hook-bearing apical portion of the leaf, the cirrus, and also, in the case of Calamus a very much modified long and very thin inflorescence axis with recurved spines, the flagellum, that is adnate to the leaf sheath. Although remarkably tenacious (Calamus is sometimes called the lawyer vine, because once you are caught by the the flagellum, it can be very difficult to get free), both eventually fall off with the leaves, and the climbing stems, which can reach lengths of up to some 200 m, tend to sag (Isnard & Rowe 2008 for details).

Economic Importance. Cocos nucifera. There is much debate as to the place of origin of the genus, Gunn (2004) suggesting that it it might be sister to the New World Parajubaea and at least 22 million years old, while Meerow et al. (2009) found a sister relationship with the New World Syagrus and suggesting its origin there some 27 million years ago. On the other hand, Kapgate (2009) found fruits in the Deccan Intertrappean Beds that are of Late Cretaceous - Early Tertiary age (see also Gómez-Navarro et al. 2009 for additional references) and Gómez-Navarro et al. (2009) found fruits that they compared with Cocos from northern Colombia that are perhaps a little younger - about 58 million years old...

Chemistry, Morphology, etc. Horn et al. (2008, esp. 2009b) look at various aspects of lamina anatomy in the context of the phylogeny of the family; this has in part been integrated above, but there is widespread homoplasy in the characters, so Horn et al. (2009b) should be consulted for details, as well as for the functional implications of their findings. According to Arber (1925), the vascular bundles are not amphivasal. Microsporogenesis is simultaneous in some Coryphoideae and Arecoideae (Harley 1999a; Sannier et al. 2006). The flower in general (e.g. Rudall et al. 2003b) and pollen in particular (see Harley 1999b; Harley & Baker 2001) is remarkably variable. The stamens are never adnate to the corolla/inner tepals in staminate flowers, although in carpellate flowers of Roystonea the corolla has a broad staminal cup at the base. In Voaniola n = 298 or more.

Additional information may be found in Corner (1966: general, a classic), Uhl (1972: Nypa), Tomlinson (1970: vascular organization in the stem), Uhl and Moore (1971), Moore (1973), Uhl and Dransfield (1987: general, particularly valuable), Zona (1997: general, esp. south east U.S.A.), Seubert (1998 and references: root anatomy), Dransfield and Uhl (1998: general), Harley and Dransfield (2003: triporate pollen), Zona (2004: embryo raphides), Prychid et al. (2004) and Piperno (2006), both SiO₂ bodies/phytoliths, Tomlinson (2006a: general), Bjorholm et al. (2006: patterns of subfamilial diversity in neotropical subfamilies, the Antilles excluded), Henderson (2006: very detailed descriptions of germination, not integrated with phylogeny), Gunawardena and Dengler (2006: leaf development), Sannier et al. (2007: microsporogenesis evolution, Ceroxyloideae not included), Svenning et al. (2008: diversity of palms in New World), Dransfield et al. (2008: invaluable - general), and Angyalossy et al. (2008: secondary thickening).

Phylogeny. [Nypoideae + Calamoideae (strong support for that clade) + the rest of the family (moderate support)] formed a trichotomy in a three-gene study by Asmussen et al. (2000); other characters supported these general relationships. Soltis et al. (3007a) recovered a well-supported clade [Nypoideae + Calamoideae]. However, details of the relationships of Nypoideae and Calamoideae to the rest of the family were unclear in other studies, although Calamoideae were probably sister to all other Arecaceae, and some morphological groupings were not supported by molecular data (Hahn 2002a, b; see also Baker et al. 1999a; Asmussen & Chase 2001; Lewis & Doyle 2001). Henderson and Stevenson (2006), after a analysis of morphological and anatomical features for selected genera, discussed groupings, relationships and character evolution. They found that Phoenix and Thrinax appear as successively sister to the rest of the family, which seemed even then rather unlikely. Asmussen et al. (2006: very good generic-level sampling, four genes) clarified this confusion and presented the rather well supported set of relationships summarized in the tree here; those parts less well supported (the monophyly of Ceroxyloideae and Arecoideae) were strongly supported by low copy nuclear DNA data (W. J. Baker, unpubl. data, in Asmussen et al. 2006). These relationships were confirmed in the comprehensive analysis of Baker et al. (2009), althouh the position of Nypoideae was not so strongly supported as that of the other subfamilies.

For morphology, phylogeny and classification in Calamoideae, see Baker et al. (1999b, 2000a, b, c). Coryphoideae include Arecoideae-Caryoteae, previously placed in Arecoideae (Uhl and Dransfield 1987; see also Dransfield et al. 2008a for a phylogeny). Ceroxyloideae include Phytelephantoideae (Dransfield et al. 2005). Phytelephas and its relatives have 4-merous flowers with up to 1000 centrifugal stamens (Palandra) and 10 carpels; Palandra also has monopodial flower clusters, unique in the family.

Gunn (2004) provides a phylogeny of Cocoeae and Lewis and Doyle (2002) and Baker et al. (2006) that of Areceae; Norup et al. (2006) discuss generic limits in Areceae, most members of which have a distinctive crown shaft (tribal apomorphy). Cuenca and Asmussen-Lange (2007) and Cuenca et al. (2007, 2008) discuss the phylogeny and biogeography of the largely New World understorey Chamaedoreeae; for the phylogeny of Chamaedorea, see Thomas et al. (2006).

Classification. Dransfield et al. (2008, see also Dransfield et al. 2005) present the outline classification followed here, but with many more details. Arecoideae here are the Arecoideae of Uhl and Dransfield (1987), but minus Caryoteae, and they also include Ceroxyloideae-Hyophorbeae (Hahn 2002b; also Baker et al. 1999a), basically, the arecoid line of Moore (1973: see Dransfield et al. 2005). Govaerts and Dransfield (2005) provide a checklist for the family, for which, see also the World Checklist of Monocots.

Botanical Trivia. Arecaceae have the largest leaf - Raphia sp., ca 25 x 3 m; the largest inflorescence - Corypha umbraculifera, ca 7.5 m long with some 10,000,000 flowers and 5280 m of flower-bearing axes (Tomlinson & Soderholm 1975); the largest seed - Lodoicea maldavica, to 50 cm long and 15-30 kg, which in turn produces the longest cotyledon, or, strictly speaking, an apocole or elongated, unifacial, non-photosynthetic part of the cotyledonary hyperphyll - this may be "several yards" or "twelve feet or more" long (Thiselton-Dyer 1910); the longest stems, perhaps up to 200 m long in Calamus manan; and the oldest functioning xylem elements and sieve tubes - palms can be hundreds of years old, and there is no secondary thickening. They also have close to the oldest viable seeds, since a seed of Phoenix dactylifera perhaps 2,000 years old has recently been germinated (Sallon et al. 2008; see also Kew Magazine, Winter 2008: 28-31).