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The families of flowering plants.                                                                                                                                                                

Trichopodaceae Hutch.

                        

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~Dioscoreaceae

IncludingAvetraceae

Habit and leaf form. Erect, tufted, forest-floor herbs (of peculiar form, with a rosette of shortish, erect aerial stems arising from the rhizome, each bearing a single, terminal leaf which subtends 1–3 long-pedicelled flowers). Perennial; shortly rhizomatous. Leaves alternate; spiral; flat; petiolate; simple. Lamina entire; lanceolate, or ovate; pinnately veined, or palmately veined, or parallel-veined (with 3–5 main veins); cross-venulate; attenuate at the base. Leaves eligulate. Lamina margins entire; flat.

Leaf anatomy. Stomata present; anomocytic.

Stem anatomy. Secondary thickening absent.

Reproductive type, pollination. Plants hermaphrodite. Pollination entomophilous.

Inflorescence, floral, fruit and seed morphology. Flowers solitary, or aggregated in ‘inflorescences’ (then of 2–3 long-pedicelled flowers, arising close together in the axil). Inflorescences at the base of the single petioles, atop the aerial stems. Flowers bracteate (at the base of the petiole); regular; 3 merous; cyclic; pentacyclic. Perigone tube present (campanulate).

Perianthof ‘tepals’; 6; joined; 2 whorled (3+3); isomerous; petaloid (the tube green, but the lobes coloured); similar in the two whorls; dark purple, or brown; persistent.

Androecium 6. Androecial members adnate (to the perigone, at the base of the segments); all equal; free of one another; 2 whorled (3+3). Androecium exclusively of fertile stamens. Stamens 6; diplostemonous; presumably alterniperianthial; shortly filantherous. Anthers basifixed; non-versatile; dehiscing via longitudinal slits; introrse; bilocular (the locules widely separated by the massive connective); tetrasporangiate; conspicuously appendaged. The anther appendages apical (subulate, by long extension of the thick connective). Endothecium developing fibrous thickenings. Anther epidermis persistent. Microsporogenesis successive. The initial microspore tetrads tetrahedral, or isobilateral, or decussate, or linear. Anther wall initially with one middle layer. Tapetum glandular. Pollen shed as single grains. Pollen grains aperturate; sulcate; 2-celled.

Gynoecium 3 carpelled. Carpels isomerous with the perianth. The pistil 3 celled. Gynoecium syncarpous; synstylovarious; inferior. Ovary 3 locular. Epigynous disk absent. Gynoecium stylate. Styles 1; apical; short, thick. Stigmas 3 (short, individually bifid, reflexed). Placentation axile. Ovules 2 per locule; funicled; pendulous; superposed; anatropous; bitegmic; tenuinucellate. Outer integument contributing to the micropyle. Embryo-sac development Polygonum-type. Antipodal cells formed; 3; not proliferating; ephemeral. Synergids hooked. Hypostase present. Endosperm formation nuclear. Embryogeny solanad (?).

Fruit slightly fleshy; indehiscent; a berry (trigonous, with a thick pericarp and three thick wings). Seeds endospermic. Endosperm ruminate (and cartilaginous). Seeds ovate, dorsally grooved, rugose. Embryo well differentiated (but minute). Cotyledons 1 (lateral, the plumule nearly terminal). Embryo straight. Testa without phytomelan; very thin. Micropylezigzag.

Geography, cytology. Paleotropical. Tropical. Southern India, Ceylon, Malay Peninsula.

Taxonomy.Subclass Monocotyledonae. Dahlgren et al. Superorder Liliiflorae; Dioscoreales. APG 3 core angiosperms; Superorder Lilianae; non-commelinid Monocot; Order Dioscoreales (as a synonym of Dioscoreaceae).

Species 2. Genera 2; Avetra, Trichopus.

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