Bulbostylis trabeculata C.B.Clarke ex Rendle

J. Browning, K.D. Gordon-Gray†, M. Lock, H. Beentje, K. Vollesen, K. Bauters, C. Archer, I. Larridon, M. Xanthos, P. Vorster, J. Bruhl, K. Wilson and X. Zhang (2020). Flora Zambesiaca Volume: 14: Cyperaceae. M.Á. García, J.R. Timberlake (Eds). Kew Publish

Type

Angola, Luanda, Casanga Is., 30.iv.1854, Welwitsch 6982 (BM syntype); Luanda, Praia do Zamba Grande & Maianga d'El Rei, 13.ii.1855, Welwitsch 7000 (BM syntype, LISU); Moçamedes, Cabo Negro, R. Curoca, ix.1859, Welwitsch 6962 (LISU syntype, BM).

Morphology General Habit

Delicate annual to 15 cm tall; tunic of leaf bases and rhizome lacking

Morphology Leaves

Leaves numerous, 1/3 to occasionally equalling culm length; leaf sheath pale brown, mouth conspicuously long white- fringed, ligule 0; leaf blades to 50 × 0.2–0.3 mm, filiform, margins and midribs sparsely scabrid

Morphology Culms

Culms ridged and furrowed, glabrous

Morphology Reproductive morphology Inflorescences

Inflorescence a small head, c. 5 mm wide, chestnut coloured, of 3–4(8) sessile spikelets; bracts 2–3, filiform, longest 10–20 mm long

Morphology Reproductive morphology Inflorescences Spikelets

Spikelets 2–5 × 1.5–2 mm, narrowly elliptic. Glumes spiral, 1.5–1.7 mm long, ovate, acuminate, pubescent, margins ciliate, 3-nerved green keel, mucronate

Morphology Reproductive morphology Flowers Androecium Stamens

Stamens (1)2–3

Morphology Reproductive morphology Flowers Gynoecium Style

Style glabrous, dark brown basally, rounded, vertically flattened, persistent on nutlet, branches 3, usually shorter than style

Morphology Reproductive morphology Fruits

Nutlet subtrigonous, obovoid, pale grey-brown at maturity, 0.5–0.6 × 0.4–0.5 mm, surface trabeculate, giving a distinctive pattern.

Distribution

Botswana, Zimbabwe. Also Kenya, Angola and Namibia.

Ecology

In Acacia woodland and on Kalahari sand in Botswana where it can provide up to 10% of ground cover in localities, or in damp sand by rivers and other water bodies; 550–1000 m.

Conservation

Widespread; not threatened.

Recognition

Plants resemble Bulbostylis barbata (Rottb.) C.B. Clarke, but the nutlet is different. They may also be confused with B. buchananii which has a similar inflorescence in which the involucral bracts tend to spread out on either side of the inflorescence head, while in B. trabeculata one bract is often longer than the others and may be held in an upright position overtopping the spikelets.

IUCN Red List of Threatened Species https://www.iucnredlist.org/species/185393/84267827

Conservation

DD - data deficient

Cyperaceae, K Hoenselaar, B. Verdcourt & H. Beentje. Hypolytrum, D Simpson. Fuirena, M Muasya. Flora of Tropical East Africa. 2010

Type

Types: Angola, Loanda, Casanga Is., Welwitsch 6982 & Praia do Zamba Grande and Matanga d’el Rei, Welwitsch 7000 & Mocamedes, Cabo Negro, banks of R. Caroca, Welwitsch 6962 (LISU, syn.; BM, isosyn.; drawing of 6982, K!)

Morphology General Habit

Slender annual 3–10 cm tall with very reduced root-system.

Morphology Stem

Stems few to many, 0.2–0.3 mm wide, angular, longitudinally ridged, almost glabrous

Morphology Leaves

Leaf sheaths whitish to pale brown with long hairs at the throat; blades up to 2 cm long, 0.3 mm wide, scabrid on margins and ribs

Morphology Reproductive morphology Inflorescences

Inflorescence a small head 3–6 mm wide of 1–4 sessile spikelets.

Morphology Reproductive morphology Inflorescences Bracts

Bracts 2–3, green and filiform, the largest 0.5–2 cm long.

Morphology Reproductive morphology Inflorescences Spikelets

Spikelets 2–4 mm long, 1–1.5 mm wide.

Morphology Reproductive morphology Inflorescences Bracts Glume

Glumes reddish brown with greenish midrib, mucronate

Morphology Reproductive morphology Flowers Androecium Stamens Anthers

Anthers 0.6–0.7 mm long without a prominent connective

Morphology Reproductive morphology Fruits

Nutlet greyish, lenticular, with distinct cells, transverse, with walls raised forming 8–10 longitudinal lines on each side of nutlet.

Morphology Reproductive morphology Flowers Gynoecium Style

Style-base darker, persistent.