The Families of Flowering Plants
| The Families of Flowering Plants | |
~ Stemonaceae
Habit and leaf form. Juicy, unbranched herbs. ‘Normal’ plants. Perennial; with a basal aggregation of leaves; rhizomatous (with scale leaves on the rootstocks). Stem growth not conspicuously sympodial (in fact, monopodial). Mesophytic. Leaves alternate; long petiolate; shortly sheathing; simple. Lamina entire; ovate; convergent pinnately veined; cross-venulate; cordate. Lamina margins entire.
Leaf anatomy. Stomata present; tetracytic. Hairs present; multicellular. Multicellular hairs multiseriate.
The mesophyll containing calcium oxalate crystals. The mesophyll crystals raphides. Vessels absent.
Stem anatomy. Secondary thickening absent. Vessel end-walls scalariform.
Root anatomy. Root xylem with vessels; vessel end-walls scalariform.
Reproductive type, pollination. Plants hermaphrodite, or polygamomonoecious (? — ‘flowers wholly or partly functionally unisexual, according to Duyfjes 1992).
Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in cymes, or in racemes. Inflorescences axillary; emerging at ground level, pedunculate, compound, shorter than the leaves, the pedicels non-articulated. Flowers bracteate; bracteolate; small; regular; 5 merous; cyclic. Perigone tube present (urceolate).
Perianth of ‘tepals’; 5; joined; 1 whorled.
Androecium 5. Androecial members adnate (the connectives, the top of the perigone tube and the ovary forming a swollen disklike structure, bearing five (nectarial?) pouches each enclosing two thecae, one from each of the adjacent anthers); united with the gynoecium (the internal extensions from the staminal tube below the anthers fusing with the stigma lobes); coherent; 1 adelphous; 1 whorled. Stamens 5; isomerous with the perianth; with sessile anthers (more or less, the filaments joined laterally the beneath the anthers into a short fleshy tube, and this basal part extended to contact the stigma). Anthers basifixed; dehiscing via longitudinal slits; introrse; tetrasporangiate; unappendaged. Tapetum glandular. Pollen grains nonaperturate; 2-celled.
Gynoecium 3 carpelled. Carpels reduced in number relative to the perianth. The pistil 1 celled. Gynoecium syncarpous; synstylovarious; inferior. Ovary 1 locular. Gynoecium stylate. Styles 1; apical (short, thick). Placentation parietal (with three placentas). Ovules in the single cavity 20–50 (each placenta with ‘many’ ovules); horizontal, or ascending; arillate; anatropous; bitegmic; crassinucellate. Outer integument not contributing to the micropyle. Embryo-sac development probably Polygonum-type. Hypostase or similar structure present.
Fruit fleshy; indehiscent; a berry. Seeds copiously endospermic (with sarcotesta-like, hyaline exotestas and inflated arillodes). Endosperm not ruminate; oily. Embryo well differentiated (but minute). Cotyledons 1. Testa without phytomelan (?).
Geography, cytology. Paleotropical. Tropical. Sumatra.
Taxonomy. Subclass Monocotyledonae. Superorder Liliiflorae; Dioscoreales. APG (1998) Monocot; non-commelinoid; Pandanales (as a synonym of Stemonaceae). Species 2. Genera 1; only genus, Pentastemona.
Duyfjes (1992), van Heel (1992), Bouman and Devente (1992).
This description is offered for casual browsing only. We strongly advise against extracting comparative information from it. 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 specified attributes, summaries of attributes within groups of taxa, geographical distribution, genera included in each family, classifications (Dahlgren; Dahlgren, Clifford, and Yeo; Cronquist; APG), and notes on the APG classification.
Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 1992 onwards. The families of flowering plants: descriptions, illustrations, identification, and information retrieval. Version: 1st June 2007. http://delta-intkey.com’.