Thesium megalocarpum A.W.Hill

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

Type

Lectotype, chosen here: Namibia, Waterberg Plateau, Dinter 585 (K, lectotype).

Morphology Reproductive morphology Flowers

Flowers 1–4(6) racemosely arranged at the tips of closely leafy twiglets Flowers 1–4(6) racemosely arranged at the tips of closely leafy twiglets.

Morphology Reproductive morphology Inflorescences Bracts

Bracts 3.5–16 × 0.6–1 mm, leaf-like, adnate to very short pedicel; bracteoles 2, 2.5–7 × 0.4–1 mm Bracts 3.5–16 × 0.6–1 mm, leaf-like, adnate to very short pedicel; bracteoles 2, 2.5–7 × 0.4–1 mm.

Morphology Reproductive morphology Flowers Pedicel

Pedicels 0–1 mm long Pedicels 0–1 mm long.

Morphology Reproductive morphology Flowers Perianth

Perianth possibly greenish; tube 0.8–1.4 mm long, external glands elliptic, rather obscure; lobes 1.2–1.5 × 0.6–1 mm, triangular, subacute, white-bearded from apex Perianth possibly greenish; tube 0.8–1.4 mm long, external glands elliptic, rather obscure; lobes 1.2–1.5 × 0.6–1 mm, triangular, subacute, white-bearded from apex.

Morphology Reproductive morphology Flowers Gynoecium Style

Style 0.7–1.4 mm long; stigma reaching top of perianth tube; placenta twisted

Ecology

Shallow sand on rocky quartzite ridges or deep Kalahari Sand in woodland or scrubby grassland; palatable to cattle; 900–1300 m.

Note

The young stems, leaves and bracts of T. megalocarpum are sometimes remarkably papillose (e.g. Wild & Drummond 6902, cited above), but are commonly glabrous or show varying degrees of development of papillae or scabrid projections. Despite this variation, the species is easily recognized by its woody, twiggy habit, flowers on very short pedicels and often solitary at the tips of short closely leafy twigs (but up to 4(6) can develop), perianth lobes bearded from the apex, and remarkably large fruits with a prominent stipe. The plant is glaucous or pale green in life and may retain its colour when dry. Roessler (loc. cit.) reduced T. dinteri A.W. Hill to synonymy under T. megalocarpum, but it is a distinct species differing from T. megalocarpum, inter alia, in its flowers on pedicels c. 3–12 mm long, shorter style (c. 0.5 mm) and straight (not twisted) placenta. N.E. Brown (in Burtt Davy, Fl. Pl. Ferns Transvaal, part 2: 461 1932) effectively lectotypified the name T. dinteri by Dinter 641, from Okaruse Kalk in Namibia. There are two sheets of this collection in Zürich (Z). The other syntype, Dinter 784, has not been traced by me; it was possibly a unicate destroyed in the Berlin fire. N.E. Brown (loc. cit.) said that his new species, T. dumale was very close to Dinter 784; T. dumale has here been reduced to T. resedoides. Dinter 5440, cited by Roessler (loc. cit.) as T. megalocarpum, is T. resedoides, which should be added to the tally of species in Namibia.

Distribution

Zimbabwe Also in Angola, Namibia and South Africa (Northern Cape and North-West Provinces). BOT N, ZIM W, ZIM C, ZIM SE, ZAM S Botswana

Morphology General Habit

Perennial herb or shrub, basal parts not seen, but stems probably tufted from a woody caudex; stems 250 mm–1 m long, up to 5–8 mm in diameter, profusely branched from the base, young parts weakly ribbed by decurrent leaves, glabrous to minutely papillose, leafy. Perennial herb or shrub, basal parts not seen, but stems probably tufted from a woody caudex; stems 250 mm–1 m long, up to 5–8 mm in diameter, profusely branched from the base, young parts weakly ribbed by decurrent leaves, glabrous to minutely papillose, leafy

Morphology Leaves

Leaves ascending, main ones c. 7–35 × 0.8–1.2 mm, sometimes smaller on the flowering twiglets, passing imperceptibly into bracts, linear to acicular, elliptic to round in section, apiculate, glabrous to minutely papillose all over. Leaves ascending, main ones c. 7–35 × 0.8–1.2 mm, sometimes smaller on the flowering twiglets, passing imperceptibly into bracts, linear to acicular, elliptic to round in section, apiculate, glabrous to minutely papillose all over

Morphology Reproductive morphology Flowers Androecium Stamens

Stamens inserted at base of perianth lobes; filaments 0.3–0.5 mm long, almost or quite hidden by anthers; anthers 0.5–0.7 mm long. Stamens inserted at base of perianth lobes; filaments 0.3–0.5 mm long, almost or quite hidden by anthers; anthers 0.5–0.7 mm long

Morphology Reproductive morphology Flowers Gynoecium Pistil

Style 0.7–1.4 mm long; stigma reaching top of perianth tube; placenta twisted.

Morphology Reproductive morphology Fruits

Fruit 3–4 × 3–4 mm, light brown, strongly ribbed and reticulate, stipe 1–3 mm long, pale. Fruit 3–4 × 3–4 mm, light brown, strongly ribbed and reticulate, stipe 1–3 mm long, pale.