The families of flowering plants
Habit and leaf form. Low shrubs (the flowering stems densely white-hairy). Plants autotrophic, or partially parasitic (? - requires investigation in view of the relationship to the mostly parasitic Orobanchaceae). To about 1 m high. Divaricately branching, leptocaul. Leaves small; opposite; flat; somewhat fleshy, or herbaceous; shortly petiolate; simple; epulvinate. Lamina entire; elliptic or acicular, or oblanceolate to oblong, or ovate, or obovate (narrower in Asepalum). Leaves exstipulate. Lamina margins entire; flat.
General anatomy. Plants presumably without laticifers.
Leaf anatomy. Hairs present; eglandular, or glandular.
Reproductive type, pollination. Fertile flowers hermaphrodite. Plants hermaphrodite.
Inflorescence, floral, fruit and seed morphology. Flowers solitary; axillary (on the numerous, leafy short-shoots); bracteolate (bibracteolate, the bracteoles small, in C. somaliense hairy, reniform-orbicular, appressed to the backs of the much larger, similarly shaped sepals; in Asepalum filiform or linear and remote from the calyx); medium-sized (much exceeding the leaves); very irregular; zygomorphic. The floral irregularity involving the perianth and involving the androecium. Flowers tetracyclic. Free hypanthium absent.
Perianth with distinct calyx and corolla, or petaline (depending on whether a highly peculiar, enlarged pair of structures beneath the corolla is interpreted as calyx or bracteoles. If the latter, the calyx is either totally lacking or - in Cyclocheilon physocalyx - reduced to a disc-like rim); if partly calycine, 7, or 5 (if reduced to corolla only); 1 whorled, or 2 whorled (?); anisomerous; petaloid, or sepaloid and petaloid; interpretable as very different in the two whorls. Calyx when accepted as such, 2; 1 whorled; only very briefly, basally gamosepalous, or polysepalous; blunt-lobed. Calyx lobes markedly longer than the tube (comprising a pair of similar, reniform-orbicular to -ovate sepals which much exceed the bracteoles that are appressed to their backs below in C. somaliense, distant in Asepalum). Calyx bilabiate; accrescent. Corolla 5; 1 whorled; much exceeding the calyx, gamopetalous. Corolla lobes blunt, markedly shorter than the tube. Degree of gamopetaly about 0.7. Corolla funnel-shaped to hypocrateriform; bilabiate (the posterior lip 2-lobed, and overlapped by the anterior 3-lobed one); white, or pink, or purple, or blue; plain.
Androecium 4. Androecial members adnate; all equal to markedly unequal; free of one another; 1 whorled. Fertile stamens representing the posterior-lateral pair and the anterior-lateral pair. Stamens 4; inserted near the base of the corolla tube (included); reduced in number relative to the adjacent perianth; oppositisepalous; alternating with the corolla members; long filantherous (the filaments hairy). Anthers basifixed (the thecae pendulous, diverging); versatile; dehiscing via longitudinal slits; introrse; bilocular (didynamous); tetrasporangiate. Pollen grains aperturate; 3–4 aperturate; colpate.
Gynoecium 2 carpelled. Carpels reduced in number relative to the perianth. The pistil 2 celled. Gynoecium syncarpous; eu-syncarpous; superior. Ovary 1 locular, or 2 locular (sometimes incompletely). Locules without false septa. Gynoecium median. Ovary sessile. Gynoecium long stylate. Styles 1; attenuate from the ovary; apical; much longer than the ovary. Stigmas 1; 1 lobed. Placentation axile, or parietal (when locules incompletely separated). Ovules 1–5 per locule; often long funicled (the S-shaped); ascending; obliquely collateral; non-arillate; anatropous.
Fruit non-fleshy; dehiscent, or a schizocarp. Mericarps 2. Fruit a capsule (in Cyclocheilon: strongly laterally flattened, winged), or achene-like (in Asepalum). Capsules loculicidal. Dispersal unit the fruit. Dispersal fruit apparently falling within the enlarged calyx (which have been alternatively interpreted as bracteoles) and wind-dispersed (Sebsebe Demmisew 2004). Seeds non-endospermic. Testa smooth (striate); brown.
Geography, cytology. Holarctic. Temperate and sub-tropical. Tunisia to Tanganyika, Arabia, Iraq.
Taxonomy. Subclass Dicotyledonae; presumably Tenuinucelli. Dahlgrens Superorder Lamiiflorae; Scrophulariales. Cronquists Subclass Asteridae; Scrophulariales. APG 3 core angiosperms; Superorder Asteranae; lamiid; Order Lamiales (in Orobanchaceae).
Species 4. Genera 2; Cyclocheilon (3 spp.) and Asepalum (1 sp.).
General remarks. Long considered a classificatory puzzle, with special reference to the very peculiar bracteoles and calyx, these genera have variously been referred previously to Verbenaceae, Scrophulariaceae, Dicrastylidaceae. DNA evidence suggests that they are embedded within Orobanchaceae sensu lato, albeit as a distinct clade (Morawetz et al. 2010) and the family remains unplaced in any formal classification. The present description (TDM, 2017) is compiled from Marais (1981), Olivers account in Hook. Ic. Pl. 25 (1896) of C. somaliense, and Stapfs of C. minutibracteolatum (= Asepalum eriantherum) in Hook. Ic. Pl. 27 (1899).
Illustrations. • Cyclocheilon somaliense: Hook. Ic. Pl.25 (1896). • Asepalum eriantherum , as Cyclocheilon minutibracteolatum: Hook. Ic. Pl. 27 (1899).
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: 20th July 2017. delta-intkey.com/angio’.