Family Centrolepidaceae
Centrolepidaceae Desv.Including Devauxiaceae Dum.Excluding Hydatellaceae Habit and leaf form. Grass- or mosslike herbs. Annual, or perennial; with a basal aggregation of leaves (when annual), or with neither basal nor terminal aggregations of leaves. Leaves alternate; spiral; sessile; sheathing. Leaf sheaths with free margins. Leaves edgewise to the stem (rarely), or with ‘normal’ orientation; simple. Lamina entire; setaceous, or linear; parallel-veined. Leaves ligulate, or eligulate; with a persistent basal meristem, and basipetal development. General anatomy. Plants with silica bodies (?), or without silica bodies. Chlorenchyma without ‘peg cells’. Accumulated starch other than exclusively ‘pteridophyte type’. Leaf anatomy. Epidermis without differentiation into ‘long’ and ‘short’ cells; containing silica bodies (? — Gaimardia), or without silica bodies. Stomata present; paracytic. Guard-cells ‘grass type’ (according to the text of Dahlgren et al. (1985), though their illustration of Pseudalepyrum depicts them otherwise). The mesophyll without calcium oxalate crystals. Vessels present; end-walls scalariform. Stem anatomy. Secondary thickening absent. Xylem with vessels. Vessel end-walls scalariform. Sieve-tube plastids P-type; type II. Root anatomy. Root xylem with vessels (sought only in Pseudalepyrum); vessel end-walls scalariform. Reproductive type, pollination. Plants monoecious, or andromonoecious, or polygamomonoecious. Gynoecium of male flowers pistillodial. Floral nectaries absent (nectaries absent). Pollination anemophilous. Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in ‘spikelets’ (each ‘pseudanthium’ being borne within two or more glumelike bracts). The ultimate inflorescence unit cymose. Inflorescences pseudanthial (as currently interpreted, the bisexual and female heads of Centrolepis and Gaimardia being seen as unisexual and bisexual aggregations of flowers, each of the latter being reduced to either one stamen or one carpel). Flowers bracteate; bracteolate (the flowers sometimes with thin subtending ‘bractlets’), or ebracteolate; small. Perianth absent. Androecium 1 (constituting the male flower, as here interpreted); exclusively of fertile stamens. Stamens 1. Anthers dorsifixed; versatile; dehiscing via longitudinal slits; bisporangiate. Microsporogenesis successive. Pollen grains aperturate; 1 aperturate; ulcerate. The ulcus without an operculum (and with no vestiges of an operculum); without an annulus. Interapertural exine scrobiculate. Interapertural interstitium granulate. Pollen grains 2-celled. Gynoecium 1 carpelled (constituting the female flower). The pistil 1 celled. Gynoecium monomerous; of one carpel; superior. Carpel 1 ovuled. Placentation apical. Ovary stipitate. Ovules pendulous; non-arillate; orthotropous; bitegmic; tenuinucellate. Outer integument contributing to the micropyle. Embryo-sac development Polygonum-type (the ‘Poaceae variant’). Antipodal cells formed; 3; not proliferating. Synergids non-haustorial. Hypostase present. Endosperm formation helobial. Embryogeny onagrad. Fruit non-fleshy. The fruiting carpel dehiscent; a follicle (tiny). Gynoecia of adjoining flowers combining to form a multiple fruit (the collective fruits capsule-like). Dispersal unit the seed. Seeds copiously endospermic. Endosperm not oily (starchy). Perisperm absent. Seeds with starch. Embryo rudimentary at the time of seed release (minute, obconical). Testa without phytomelan; thin. Seedling. Hypocotyl internode absent. Seedling collar not conspicuous. Cotyledon hyperphyll elongated; assimilatory; more or less circular in t.s. Coleoptile absent. Seedling cataphylls absent. First leaf centric. Primary root ephemeral. Physiology, biochemistry. Not cyanogenic. Aluminium accumulation demonstrated (Centrolepis). Geography, cytology. Temperate to tropical. Southeast Asia and Australasia. X = 10–13. Taxonomy. Subclass Monocotyledonae. Dahlgren et al. Superorder Commeliniflorae; Poales. APG 3 core angiosperms; Superorder Lilianae; commelinid Monocot; Order Poales. Species 40. Genera 5; Aphelia, Brizula, Centrolepis, Gaimardia, Pseudalepyrum. Illustrations. |
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