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The families of flowering plants

L. Watson and M.J. Dallwitz

Corsiaceae Becc.

~ Burmanniaceae, Orchidaceae.

Including Achratinitaceae Barkley

Habit and leaf form. Reduced herbs. Leaves much reduced (to scales). Plants parasitic; mycoheterotrophic; not green. Perennial; rhizomatous, or tuberous. Mesophytic. Leaves small; alternate; spiral; membranous; sessile; sheathing; simple; epulvinate. Lamina entire; parallel-veined; without cross-venules.

General anatomy. Plants without silica bodies.

Leaf anatomy. Stomata anomocytic.

Axial (stem, wood) anatomy. Cork cambium absent. Secondary thickening absent.

Reproductive type, pollination. Plants hermaphrodite (Corsia), or monoecious.

Inflorescence, floral, fruit and seed morphology. Flowers solitary; terminal; ebracteate; very irregular; zygomorphic. The floral irregularity involving the perianth. Flowers 3 merous; cyclic. Perigone tube present.

Perianth of ‘tepals’; 6; joined; 2 whorled (3+3); isomerous; petaloid; different in the two whorls (in that the posterior member of the outer whorl is large and coloured, and encloses the other five, which are linear-spathulate).

Androecium 6. Androecial members free of the perianth; free of one another; 2 whorled. Androecium exclusively of fertile stamens. Stamens 6; diplostemonous. Anthers dehiscing via longitudinal slits; extrorse. Microsporogenesis successive. Pollen shed as single grains. Pollen grains aperturate; 1 aperturate; sulcate, or ulcerate.

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 (thick). Placentation parietal (the three placentae more or less intruded, two-lobed). Ovules in the single cavity 25–100 (i.e. ‘many’); anatropous; bitegmic; tenuinucellate. Embryo-sac development Polygonum-type. Endosperm formation helobial.

Fruit non-fleshy; dehiscent; a capsule. Capsules valvular. Fruit 25–100 seeded (‘many’). Seeds endospermic. Endosperm oily, or not oily. Seeds minute, or small; winged. Embryo rudimentary at the time of seed release. Testa without phytomelan.

Geography, cytology. Australian and Antarctic. Sub-tropical to tropical. New Guinea, Australia, Solomon Is., Chile. X = 9.

Taxonomy. Subclass Monocotyledonae. Dahlgren et al. Superorder Liliiflorae; Burmanniales. APG III core angiosperms; Superorder Lilianae; non-commelinid Monocot. APG IV Order Liliales.

Species 10. Genera 2; Corsia, Arachnitis.

Illustrations. • Arachnitis uniflora and Corsia ornata: Nat. Pflanzenfam. (1889). • Corsia cordata: Schlechter (1913).

We advise against extracting comparative information from the descriptions. This is much more easily achieved using the DELTA data files or the interactive key, which allows access to the character list, illustrations, full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, distributions of character states within any set of taxa, geographical distribution, genera included in each family, and classifications (Dahlgren; Dahlgren, Clifford, and Yeo; Cronquist; APG). See also Guidelines for using data taken from Web publications.

Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 1992 onwards. The families of flowering plants: descriptions, illustrations, identification, and information retrieval. Version: 15th April 2018.’.