Thesium dissitum N.E.Br.

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

Type

Type:Botswana, in the Kalahari Desert near Mamunwe, 26.ii.1897, E.J. Lugard 239 (K, holotype).

Morphology General Habit

Perennial with a woody taproot up to c. 10 mm diameter at the crown; stems several tufted from the crown, c. 150–450 mm long, erect or possibly sometimes spreading, well branched from the base, branches ascending, ribbed by decurrent leaves, leafy Perennial with a woody taproot up to c. 10 mm diameter at the crown; stems several tufted from the crown, c. 150–450 mm long, erect or possibly sometimes spreading, well branched from the base, branches ascending, ribbed by decurrent leaves, leafy.

Morphology Leaves

Leaves ascending to spreading, primary ones on main stems c. 15–45 × 0.8–1.3 mm, shorter upwards and passing into bracts, linear, apex apiculate, margins cartilaginous, very minutely scabridulous to smooth Leaves ascending to spreading, primary ones on main stems c. 15–45 × 0.8–1.3 mm, shorter upwards and passing into bracts, linear, apex apiculate, margins cartilaginous, very minutely scabridulous to smooth.

Morphology Reproductive morphology Flowers

Flowers either solitary in the axil of each bract or in 3-flowered cymules, c. 5–15 racemosely arranged, inflorescences lax, sometimes with cymules in lower part, solitary flowers in upper, though terminating in a cymule Flowers either solitary in the axil of each bract or in 3-flowered cymules, c. 5–15 racemosely arranged, inflorescences lax, sometimes with cymules in lower part, solitary flowers in upper, though terminating in a cymule.

Morphology Reproductive morphology Flowers Pedicel

Pedicels/peduncles 2–15 mm long

Morphology Reproductive morphology Flowers Gynoecium Style

Style 0.4–0.9 mm long; stigma reaching top of tube

Ecology

Brachystegia and other mixed woodland; c. 900–1400 m.

Note

Thesium dissitum seems to be very close to T. mukense: both have long leaves and long bracts adnate up to the bracteoles, but T. dissitum has a woody taproot while T. mukense has woody stolons, and the pedicels/peduncles of T. dissitum are mostly longer than those of T. mukense. N.E. Brown quoted the type of T. dissitum as having come from the Kalahari Desert near Mamunwe, a name not traced, nor is Lugard's route when he visited Lake Ngami clear to me, though he is known to have collected along the Boteti R. and around the Khwebe Hills. The specimen comprises four short, closely leafy stems just coming into flower; the most striking features are the long leaves, long bracts adnate to the pedicels right up to the bracteoles and far overtopping the flowers, which are borne either singly or in 3-flowered cymules in the axil of each bract, with at least 15 pedicels/peduncles in the inflorescence. The material here associated with the type agrees in all these essential features but nevertheless I am not satisfied that it is homogeneous. For example, Fanshawe 10177 (cited above) comprises two old twigs with a galled fruit, and a few young flowers; the leaves are patent to reflexed, while they are ascending in all other specimens seen. Banda 137 (also cited above) differs in having leaves mostly shorter than usual. Another specimen (Barbosa 1451, LISC, from Rutanda in Mozambique, near the Zimbabwean border at Mutare) is in the affinity of T. dissitum but has bracts and pedicels rather short for that species; no primary leaves remain. Clearly, before T. dissitum can be fully understood, many more good collections are needed, over a wide geographical area.

Distribution

Mozambique Malawi Zimbabwe Zambia BOT N, ZAM N, ZAM S, ZIM N, ZIM C, ZIM W, MAL S, MOZ T Botswana Not known elsewhere.

Morphology Reproductive morphology Inflorescences Bracts

Bracts 8–23 × 0.5–1.2 mm, linear, leaf-like, sometimes adnate to entire pedicel but only to lower part of peduncle in a single inflorescence, or wholly adnate (partial adnation in longest peduncles); bracteoles 2, c. 4–9 × 0.5–0.8 mm. Bracts 8–23 × 0.5–1.2 mm, linear, leaf-like, sometimes adnate to entire pedicel but only to lower part of peduncle in a single inflorescence, or wholly adnate (partial adnation in longest peduncles); bracteoles 2, c. 4–9 × 0.5–0.8 mm

Morphology Reproductive morphology Flowers Pedicels and Peduncles

Pedicels/peduncles 2–15 mm long.

Morphology Reproductive morphology Flowers Perianth

Perianth probably yellowish-green; tube 0.6–0.9 mm long, external glands ellipsoid, inconspicuous; lobes 1.2–1.4 × 0.6–0.8 mm, triangular, acute, white-bearded from the apex. Perianth probably yellowish-green; tube 0.6–0.9 mm long, external glands ellipsoid, inconspicuous; lobes 1.2–1.4 × 0.6–0.8 mm, triangular, acute, white-bearded from the apex

Morphology Reproductive morphology Flowers Androecium Stamens

Stamens inserted at base of perianth lobes; filaments 0.2–0.5 mm long, hidden by anthers; anthers 0.3–0.6 mm long. Stamens inserted at base of perianth lobes; filaments 0.2–0.5 mm long, hidden by anthers; anthers 0.3–0.6 mm long

Morphology Reproductive morphology Flowers Gynoecium Pistil

Style 0.4–0.9 mm long; stigma reaching top of tube.

Morphology Reproductive morphology Fruits

Fruit 2.5–3 × 2.5–3 mm, light brown, strongly ribbed and reticulate. Fruit 2.5–3 × 2.5–3 mm, light brown, strongly ribbed and reticulate.