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The families of flowering plants

L. Watson and M.J. Dallwitz

Geosiridaceae Jonker

~ Iridaceae.

Habit and leaf form. Small, colourless herbs (lacking rhizomes and corms, the scaly, basal part of the stem with mycorrhizal roots). Leaves well developed. Plants parasitic; mycoheterotrophic; not green. Leaves small (reduced); alternate; membranous; simple. Lamina entire. Lamina margins entire.

Axial (stem, wood) anatomy. Secondary thickening presumably absent.

Reproductive type, pollination. Plants hermaphrodite.

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in cymes. The ultimate inflorescence units cymose. Flowers bracteate; small; regular; cyclic; tetracyclic. Perigone tube present (short).

Perianth of ‘tepals’; 6; joined; 2 whorled (3+3, the outer imbricate, the inner contorted); isomerous; petaloid; similar in the two whorls; blue (-ish).

Androecium 3. Androecial members adnate (to the base of the perianth); all equal; free of one another; 1 whorled. Androecium exclusively of fertile stamens. Stamens 3; isomerous with the perianth; alterniperianthial (opposite the outer perianth segments); very shortly filantherous. Anthers basifixed (oblong); non-versatile; dehiscing via longitudinal slits; extrorse; tetrasporangiate. Pollen shed as single grains. Pollen grains aperturate; 1 aperturate (sulcoidate).

Gynoecium 3 carpelled. Carpels isomerous with the perianth. The pistil 3 celled. Gynoecium syncarpous; synstylovarious, or eu-syncarpous (?); inferior. Ovary 3 locular. Epigynous disk absent. Gynoecium stylate. Styles 1 (tribrachiate); apical. Stigmas 3. Placentation axile (the placentas branched, intruding).

Fruit non-fleshy; dehiscent, or indehiscent (?); a capsule, or capsular-indehiscent (?—with an annulus which may be marcescent). Capsules circumscissile (triangular-obconical). Seeds minute. Testa without phytomelan (?).

Geography, cytology. Paleotropical. Tropical. Madagascar, Comoros Archipelago.

Taxonomy. Subclass Monocotyledonae. Dahlgren et al. Superorder Liliiflorae; Liliales (cf. Iridaceae and Burmanniaceae?). APG III core angiosperms; Superorder Lilianae; non-commelinid Monocot. APG IV Order Asparagales (as a synonym of Iridaceae).

Species 2 (Geosiris aphylla, G. albiflora). Genera 1; only genus, Geosiris.

General remarks. This description is rather inadequate, but differs from that of Iridaceae (q.v.) in leaf, inflorescence and fruit characters, as well as the mycoheterotrophic habit.

Illustrations. • Geosiris aphylla, with Iridaceae: Humbert, Flora Madagascariensis (1946).

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.’.