Stemonaceae Engl.
Including Croomiaceae Nak., Roxburghiaceae Wallich
Excluding Pentastemonaceae
Habit and leaf form. Herbs, or lianas (or shrublets). Plants non-succulent. Perennial; with neither basal nor terminal aggregations of leaves; rhizomatous, or tuberous. Self supporting, or climbing; sometimes stem twiners; Stemona twining anticlockwise. Mesophytic. Leaves alternate, or opposite, or whorled; when alternate, distichous; ‘herbaceous’, or leathery; petiolate; non-sheathing; simple. Lamina entire; convergent palmately veined; cross-venulate; cordate (often), or attenuate at the base, or rounded at the base. Lamina margins entire.
Leaf anatomy. Stomata present; anomocytic.
Vessels absent.
Stem anatomy. Primary vascular tissue comprising a ring of bundles, or in two or more rings of bundles. Secondary thickening absent (the vascular bundles in two concentric circles). Xylem with vessels, or without vessels. Vessel end-walls scalariform.
Root anatomy. Root xylem with vessels. Vessel end-walls scalariform.
Reproductive type, pollination. Plants hermaphrodite (usually), or monoecious. Entomophilous.
Inflorescence, floral, fruit and seed morphology. Flowers solitary, or aggregated in ‘inflorescences’; in cymes, or in racemes. The terminal inflorescence unit cymose, or racemose. Inflorescences axillary; few flowered cymes or racemes, the pedicels articulated. Flowers bracteate (and axillary), or ebracteate; small, or medium-sized; sometimes malodorous; regular; 2 merous, or 4 merous; cyclic; pentacyclic, or tricyclic. Perigone tube present, or absent.
Perianth of ‘tepals’; 4; free, or joined; 2 whorled; isomerous (2+2); sepaloid, or petaloid; similar in the two whorls.
Androecium 4. Androecial members adnate; free of one another, or coherent (Stemona, where the broad stamens are basally connate, and have an internal extension that contacts the stigma); often 1 adelphous (the filaments connate); 1 whorled, or 2 whorled. Androecium exclusively of fertile stamens. Stamens 4; diplostemonous. Anthers basifixed; dehiscing via longitudinal slits; introrse; tetrasporangiate; appendaged (apically), or unappendaged. Microsporogenesis successive. Anther wall of the ‘monocot’ type. Tapetum glandular. Pollen shed as single grains. Pollen grains aperturate, or nonaperturate; when aperturate, 1 aperturate; sulcate; 2-celled.
Gynoecium 2 carpelled. Carpels reduced in number relative to the perianth. The pistil 1 celled. Gynoecium syncarpous; synstylovarious; superior, or partly inferior (Stichoneuron). Ovary 1 locular. Gynoecium non-stylate, or stylate. Styles apical. Placentation basal (Stemona), or apical (Stichoneuron). Ovules in the single cavity 3–50 (‘few to several’, or ‘many’); horizontal, or ascending; arillate; orthotropous, or anatropous; bitegmic; crassinucellate. Outer integument not contributing to the micropyle. Embryo-sac development Polygonum-type. Polar nuclei fusing only after one has been fertilized, or fusing simultaneously with the male gamete (?). Antipodal cells formed; 3; not proliferating; very ephemeral. Synergids hooked (with filiform apparatus). Endosperm formation nuclear. Embryogeny asterad.
Fruit non-fleshy; dehiscent, or indehiscent; a capsule, or capsular-indehiscent. Capsules sometimes two valvular. Seeds endospermic. Endosperm not ruminate; oily. Testa without phytomelan.
Seedling. Hypocotyl internode absent. Seedling collar not conspicuous. Cotyledon hyperphyll compact; non-assimilatory. Coleoptile absent. Seedling cataphylls present (above the first leaf). First leaf dorsiventral. Primary root persistent.
Physiology, biochemistry. Not cyanogenic. Alkaloids present (6 species).
Geography, cytology. Holarctic, Paleotropical, and Australian. Sub-tropical to tropical. Southeast Asia, Malaysia, Northern Australia. X = 7.
Taxonomy. Subclass Monocotyledonae. Superorder Liliiflorae; Dioscoreales. APG (1998) Monocot; non-commelinoid; Pandanales. Species 23. Genera 3; Croomia, Stemona, Stichoneuron.
Illustrations. • Technical details (Stemona).
Cite this publication as: ‘L. Watson and M. J. Dallwitz (1992 onwards). The Families of Flowering Plants: Descriptions, Illustrations, Identification, and Information Retrieval. Version: 14th December 2000. http://biodiversity.uno.edu/delta/’. Dallwitz (1980), Dallwitz, Paine and Zurcher (1993, 1995, 2000), and Watson and Dallwitz (1991) should also be cited (see References).
