The families of flowering plants

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L. Watson and M. J. Dallwitz

Thurniaceae Engl.

Habit and leaf form. Large, tough herbs. ‘Normal’ plants, or switch-plants (? — cf. the peculiar leaf blade vascularization). With a basal aggregation of leaves; rhizomatous. Leaves alternate; four-ranked, or tristichous; flat (or canaliculate); leathery; sessile; sheathing; simple. Lamina entire; linear; parallel-veined. Lamina margins minutely serrate, or entire. Leaf development presumably ‘graminaceous’.

General anatomy. Plants with silica bodies (spheroidal, in the epidermis and parenchyma).

Leaf anatomy. The leaf lamina having the vascular bundles arranged in vertical pairs, with the phloem orientated to the inside — i.e., the upper bundles ‘normal’, the lower ‘inverted’. Epidermis containing silica bodies. Stomata present; paracytic, or tetracytic. The mesophyll not containing mucilage cells; without crystals. Foliar vessels present; with scalariform end-walls.

Axial (stem, wood) anatomy. Young stems bluntly tetragonal, or triangular in section. Secondary thickening absent.

The vessel end-walls oblique; scalariform, or scalariform and simple (mainly scalariform).

Root anatomy. Root xylem with vessels (perforation plates scalariform).

Reproductive type, pollination. Plants hermaphrodite. Floral nectaries absent (no nectaries). Pollination anemophilous.

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in heads (densely concentrated). The ultimate inflorescence units (the heads) racemose. Inflorescences of one or several heads; with involucral bracts; pseudanthial. Flowers small (with short, swollen, puberulous pedicels); regular; 3 merous; cyclic. Perigone tube absent. Hypogynous disk absent.

Perianth of ‘tepals’; 6; free; 2 whorled (3+3); isomerous; sepaloid, or petaloid (the members thin, narrow, hyaline, persistent, obtuse); similar in the two whorls (chaffy); hyaline; persistent.

Androecium 6. Androecial members free of the perianth to adnate (the filaments somewhat adnate to the tepals at their bases); free of one another; 2 whorled (3+3). Androecium exclusively of fertile stamens. Stamens 6; diplostemonous; filantherous (the filaments thin and relatively long). Anthers basifixed; dehiscing via longitudinal slits; tetrasporangiate. Pollen shed in aggregates; in tetrads (tetrahedral). Pollen grains aperturate; 1 aperturate; ulcerate (cf. Juncaceae).

Gynoecium 3 carpelled. Carpels isomerous with the perianth. The pistil 3 celled. Gynoecium syncarpous; synovarious to synstylovarious (short styled, with three long stigmatic branches); superior. Ovary 3 locular. Gynoecium shortly stylate. Styles 1; attenuate from the ovary; apical. Stigmas 3. Placentation basal, or axile. Ovules 1–7 per locule (to ‘several’); ascending; apotropous; anatropous.

Fruit non-fleshy; dehiscent; a capsule. Capsules loculicidal. Fruit triangular, 3 seeded. Seeds endospermic (the nucellus and enclosed endosperm free from the seed coat, except at the micropylar end); conspicuously hairy (hispid); winged (with a hispid, subulate process at each end). Embryo small, well differentiated. Cotyledons 1. Embryo cylindrical, straight. Testa without phytomelan; brown (thick).

Physiology, phytochemistry. Not cyanogenic.

Geography, cytology. Neotropical. Tropical. Northeast Brazil, Guiana.

Taxonomy. Subclass Monocotyledonae. Dahlgren et al. Superorder Commeliniflorae; Cyperales. APG 3 core angiosperms; Superorder Lilianae; commelinid Monocot; Order Poales.

Species 3. Genera 1; only genus, Thurnia.

Illustrations. • Thurnia jenmani: Hook. Ic. Pl. 15 (1883–85). • Thurnia sphaerocephala: Hook. Ic. Pl. 15 (1883–85).

The descriptions are offered for casual browsing only. We strongly advise against extracting comparative information from them. This is much more easily achieved using 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).

Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 1992 onwards. The families of flowering plants: descriptions, illustrations, identification, and information retrieval. Version: 11th May 2015.’.