Thesium L.

Santalaceae, P.M. Polhill, B.A., Ph.D., F.L.S.. Flora of Tropical East Africa. 2005

Morphology General Habit

Shrubs or herbs

Morphology Leaves

Leaves sessile, alternate, oblong, linear or reduced to scales, 3-nerved

Morphology Reproductive morphology Flowers

Flowers hermaphrodite, axillary and terminal, solitary or in cymules; bracts generally conspicuous, often adnate to the pedicel or peduncle; bracteoles 2–several, persistent

Morphology Reproductive morphology Flowers Perianth

Perianth leathery; tube campanulate to cylindrical, often with evident glands below the sinuses of the lobes, sometimes tooth-like; lobes (3–)5, valvate, glabrous or variously fringed or bearded, the tips often hooded

Morphology Reproductive morphology Flowers Androecium Stamens

Stamens as many as the lobes, inserted on or at the base of the lobes; anthers in East African species attached to the lobes by a tuft of hairs

Morphology Reproductive morphology Flowers Disc

Disk developed to varying degrees, fleshy, lobed, lining the perianth tube

Morphology Reproductive morphology Flowers Gynoecium Pistil

Ovary with 3 ovules pendent from apex of a free-central placenta, the placenta straight or twisted; style usually evident, simple

Morphology Reproductive morphology Fruits

Fruit usually shortly stipitate, indehiscent, globose or ovoid, usually bony, 10-ribbed and ± reticulate between the ribs, or less often fleshy, crowned with the persistent perianth.

Flora Zambesiaca. Vol. 9, Part 3. Polygonaceae-Myriaceae. Pope GV, Polhill RM, Martins ES. 2006.

Morphology Reproductive morphology Inflorescences Bracts

Bract often conspicuous, often adnate to pedicel or peduncle; bracteoles 2–several, all persistent

Morphology Reproductive morphology Flowers Gynoecium Ovary

Ovary with 3 ovules pendant from apex of erect free-central placenta; placenta straight or twisted; stigma capitate; style wanting to well developed, simple, cylindric. Fruit indehiscent, globose or ovoid, usually bony, 10-ribbed, ± reticulate between ribs, crowned with a persistent perianth, subtended by a stipe.

Note

In his classification, Hill emphasized the ornamentation on the perianth lobes; a revised classification should take into account the structure of the inflorescence, as has already been suggested by Robyns & Lawalrée (in Bull. Jard. Bot. État 17: 137 (1944)). Many of the species are poorly known; field work is needed, not only to augment collections, but also to study the impact of fire on growth patterns. The possibility of hybridization should also not be overlooked. All the species in the Flora Zambesiaca area have the anthers attached to the perianth lobes by a tuft of hairs and therefore belong in sections Imberbia and Barbata of A.W. Hill (in Bull. Misc. Inform., Kew 1915: 10 (1915), and F.C. 5, 2: 137, 140 (1915)). Hendrych (in Nov. Bot. Hort. Bot. Univ. Carol. Prag.: 17 (1962)) amended Hill's infrageneric classification, partly for nomenclatural reasons. As he was largely concerned with European and Asian species and did not deal with African species in general, no infrageneric classification is used here. In any case a thorough revision of all the species is needed first.

Distribution

Over 300 species, all in the Old World, many in Africa.

Morphology General Habit

Shrubs or herbs. Shrubs or herbs

Morphology Leaves

Leaves sessile, alternate, in the Flora Zambesiaca area mostly linear or reduced to scales, ± oblong in one species, triplinerved. Leaves sessile, alternate, in the Flora Zambesiaca area mostly linear or reduced to scales, ± oblong in one species, triplinerved

Morphology Reproductive morphology Flowers

Flowers hermaphrodite, axillary and terminal, solitary or in cymules in the axils of the bracts. Flowers hermaphrodite, axillary and terminal, solitary or in cymules in the axils of the bracts

Morphology Reproductive morphology Inflorescences Bracteoles

Bract often conspicuous, often adnate to pedicel or peduncle; bracteoles 2–several, all persistent.

Morphology Reproductive morphology Flowers Perianth

Perianth leathery; tube campanulate to cylindric, often with conspicuous external glands below the sinuses of the perianth lobes, sometimes with tooth-like glands alternating with the lobes; lobes usually 5, rarely 4 or 3, valvate, glabrous or variously fringed or bearded, tips hooded. Perianth leathery; tube campanulate to cylindric, often with conspicuous external glands below the sinuses of the perianth lobes, sometimes with tooth-like glands alternating with the lobes; lobes usually 5, rarely 4 or 3, valvate, glabrous or variously fringed or bearded, tips hooded

Morphology Reproductive morphology Flowers Androecium Stamens

Stamens as many as lobes, inserted on or at base of lobes, in the Flora Zambesiaca species anthers attached to lobes by tuft of hairs. Stamens as many as lobes, inserted on or at base of lobes, in the Flora Zambesiaca species anthers attached to lobes by tuft of hairs

Morphology Reproductive morphology Flowers Disc

Disk often well developed, fleshy, lobed, lining perianth tube. Disk often well developed, fleshy, lobed, lining perianth tube

Morphology Reproductive morphology Flowers Gynoecium Pistil

Ovary with 3 ovules pendant from apex of erect free-central placenta; placenta straight or twisted; stigma capitate; style wanting to well developed, simple, cylindric.

Morphology Reproductive morphology Fruits

Fruit indehiscent, globose or ovoid, usually bony, 10-ribbed, ± reticulate between ribs, crowned with a persistent perianth, subtended by a stipe.