Thismiaceae J.G. Agardh
Habit and leaf form. Achlorophyllous herbs. Leaves much reduced. Plants succulent (somewhat), or non-succulent; saprophytic. Perennial; rhizomatous (the rhizome sometimes branched and coral-like). Mesophytic. Leaves small; alternate, or opposite; distichous; membranous; sessile; sheathing; simple. Lamina entire; parallel-veined; without cross-venules. Lamina margins entire.
Leaf anatomy. Stomata present; anomocytic.
The mesophyll containing calcium oxalate crystals. The mesophyll crystals raphides.
Stem anatomy. Secondary thickening absent.
Reproductive type, pollination. Plants hermaphrodite.
Inflorescence, floral, fruit and seed morphology. Flowers solitary, or aggregated in ‘inflorescences’; in racemes. The ultimate inflorescence unit racemose. Inflorescences scapiflorous; terminal; racemes. Flowers bracteate; small; regular to very irregular; when irregular, zygomorphic. The floral irregularity (when present) involving the perianth (the tube sometimes zygomorphic). Flowers 3 merous; cyclic; pentacyclic. Perigone tube present (circumcissile in fruit, campanulate or urceolate, the lobes sometimes sometimes linear, curved, or fused into a mitre or other strange configuration).
Perianth of ‘tepals’; 6; joined; 2 whorled; isomerous; petaloid; similar in the two whorls, or different in the two whorls (the lobes equal, or those of the inner whorl longer and narrower or even geniculate).
Androecium 6. Androecial members adnate (to the perianth tube); free of one another, or coherent (via connate filaments); when joined, 1 adelphous; 2 whorled. Stamens 6 (usually), or 3; diplostemonous (usually), or isomerous with the perianth. Anthers basifixed; non-versatile; dehiscing via longitudinal slits; introrse; bilocular (the thecae separated); appendaged (with apical enlargement of the connective). Endothecium developing fibrous thickenings. Anther epidermis persistent. Microsporogenesis successive. Pollen grains aperturate; 1 aperturate; ulcerate (at least in some genera).
Gynoecium 3 carpelled. Carpels isomerous with the perianth. The pistil 1 celled. Gynoecium syncarpous; synstylovarious; inferior. Ovary 1 locular. Gynoecium stylate. Styles 1; apical. Stigmas 3. Placentation parietal. Ovules in the single cavity 50–100 (‘many’); anatropous; bitegmic; tenuinucellate. Embryo-sac development Polygonum-type. Polar nuclei fusing prior to fertilization. Antipodal cells not formed (the three nuclei soon degenerating). Synergids pear-shaped. Endosperm formation helobial.
Fruit non-fleshy; dehiscent; a capsule. Capsules circumscissile. Fruit 50–150 seeded (‘many’). Seeds non-endospermic; minute. Embryo rudimentary at the time of seed release. Testa without phytomelan.
Seedling. Germination cryptocotylar.
Geography, cytology. Holarctic, Paleotropical, Neotropical, Australian, and Antarctic. Southeast Asia, Africa, America (mainly Brazil), Australia, New Zealand.
Taxonomy. Subclass Monocotyledonae. Dahlgren et al. Superorder Liliiflorae; Burmanniales. APG 3 core angiosperms; Superorder Lilianae; non-commelinid Monocot; Order Dioscoreales (as a synonym of Burmanniaceae).
Species 30. Genera 4; Afrothismia, Haplothismia, Oxygyne, Thismia (Geomitra, Triscyphus.