| # The Families of Angiosperms |

L. Watson and M.J. Dallwitz

### Stemonaceae Engl.

Including Croomiaceae Nak., Roxburghiaceae Wallich; excluding Pentastemonaceae.

Habit and leaf form. Herbs, or lianas, or shrubs (then ‘shrublets’); non-laticiferous, without coloured juice. Perennial; without conspicuous 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 to the base, or rounded at the base. Lamina margins entire.

Leaf anatomy. Stomata present; anomocytic. Foliar vessels absent.

Axial (stem, wood) anatomy. Primary vascular tissues comprising a ring of bundles, or comprising two or more rings of bundles. Secondary thickening absent (the vascular bundles in two concentric circles). The axial xylem with vessels, or without vessels.

The vessel end-walls scalariform.

Root anatomy. Root xylem with vessels; vessel end-walls scalariform.

Reproductive type, pollination. Unisexual flowers present, or absent. Plants hermaphrodite (usually), or monoecious. Pollination entomophilous.

Inflorescence, floral, fruit and seed morphology. Flowers solitary, or aggregated in ‘inflorescences’; when aggregated, in cymes, or in racemes. The ultimate inflorescence units 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; often conspicuously appendaged, or unappendaged. The anther appendages when present, apical. 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, phytochemistry. 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. Dahlgren et al. Superorder Liliiflorae; Dioscoreales. APG III core angiosperms; Superorder Lilianae; non-commelinid Monocot. APG IV Order Pandanales.

Species 23. Genera 3; Croomia, Stemona, Stichoneuron.

Illustrations. • Croomia pauciflora, vegetative: Tomlinson and Ayensu, J. Arnold Arb. 49 (1968). • Croomia pauciflora, flowers: Tomlinson and Ayensu, J. Arnold Arb. 49 (1968). • Croomia pauciflora, leaf anatomy: Tomlinson and Ayensu, J. Arnold Arb. 49 (1968). • Croomia pauciflora, stem and petiole anatomy: Tomlinson and Ayensu, J. Arnold Arb. 49 (1968). • Stemona curtisii: Bot. Mag. 118 (1892). • Stemona sessiliflora, as S. erecta: Hook. Ic. Pl. 24 (1895). • Stemona tuberosa, as Roxburghia gloriosoides: Lindley. • Stichoneuron membranaceum: Hook. Ic. Pl. 18 (1888).

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: 8th June 2026. delta-intkey.com’.

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