Leucas nyassae Gürke

J. R. Timberlake, E. S. Martins (2013). Flora Zambesiaca, Vol 8: part 8. Royal Botanic Gardens, Kew

Type

Types: Malawi, Shire Highlands, 1891, Buchanan 255 (B† syntype, BM, K); Shire Highlands, xii.1881, Buchanan 460 (B† syntype, K).

Morphology General Habit

Perennial herb up to 2 m high, stem erect or procumbent from a woody rootstock

Morphology Leaves

Leaves ± sessile to very shortly petiolate; blade 4–12 × 0.4–3.5 cm, narrowly elliptic, occasionally elliptic or narrowly ovate, or oblanceolate or obovate to ± linear, margin serrate to shallowly serrate throughout, or crenate in upper half or third only, apex acute to obtuse, occasionally shortly acuminate, base attenuate, upper and lower surfaces with appressed or silky spreading hairs, both hair types more plentiful beneath either obscuring surface or concentrated on raised venation, also with yellow sessile glands; petiole less than 5 mm long Leaf upper surface with appressed hairs, lower surface with appressed hairs, more plentiful on raised venation

Morphology Reproductive morphology Inflorescences

Inflorescence of 1–3 verticils spaced 25–75 mm apart, usually laxly spaced, verticils usually many-flowered, congested, or with fewer flowers and less congested; pedicel ± 1 mm long, hairy; bracteoles 8–20 mm long, linear-lanceolate to lanceolate, pubescent with long to short spreading hairs, or densely pubescent with silky hairs, sometimes midrib distinct

Morphology Reproductive morphology Flowers Calyx

Calyx tube funnel-shaped, 8–9 mm long at anthesis (whole length 12–15 mm), extending noticeably in fruit due to lengthening of anterior lip, pubescent with appressed whitish hairs, longer and more spreading on lobes, or densely pubescent with silky hairs, also with yellow sessile glands, inner surface with appressed hairs, visible on posterior side in sinuses between calyx lobes; throat asymmetric, anterior lip 2–3 mm longer than tube in flower, becoming 5–9 mm longer than tube in fruit; lobes 10, anterior lip with 3 central lobes, triangular with short subulate tips, ± 2 mm long, and 4 lateral lobes, very narrowly triangular, ± 3 mm long, posterior lip with 3 subulate lobes, 2/3 or equal in length to anterior lip, 2–3 mm in flower, 4–9 mm in fruit, centre lobe sometimes longer than other 2 Calyx tube pubescent with appressed whitish hairs, hairs longer and more spreading on lobes

Morphology Reproductive morphology Flowers Corolla

Corolla white, 15–22 mm long; tube 8–12 mm long, inner surface with strongly undulate band of short glandular hairs halfway down tube; posterior lip 7–10 mm long, anterior lip as long or slightly longer than posterior lip, 7–12 mm long, inner surface with outer surface pubescent, with yellow sessile glands Corolla outer surface densely pubescent with appressed hairs.

Morphology Reproductive morphology Fruits

Nutlets truncate at apex, with hairs and sessile glands.

Recognition

Leucas nyassae is a complex species. Sebald (1980) recognised three varieties, var. nyassae, var. velutina and var. villosa. I retain the first two here, but have reduced the third, var. villosa, to synonymy under var. nyassae. Sebald himself states that the only difference between var. nyassae and var. villosa is that the latter tends to have erectrather than procumbent stems; I do not consider this character sufficient to uphold the taxon. There is much variation within var. nyassae across its wide range, but all plants share the same shaped calyx, although it differs slightly in size. The calyx is recognisable since its posterior side has three long and narrow lobes that are almost equal in length to the anterior side, while the anterior side is noticeably accrescent in fruit. Corolla morphology is conservative within the species, its posterior lip being particularly convex and densely pubescent. Bracteole shape correlates weakly with distribution – in the Flora Zambesiaca area, plants tend to have linear, occasionally lanceolate bracteoles with long spreading hairs, while in Tanzania bracteoles are generally lanceolate with a distinct midrib. Much variation also occurs in leaf shape – specimens from the Flora area tend to have narrowly elliptic leaves and dry a brighter green colour, while specimens from Tanzania are more likely to have oblanceolate or even linear leaves and dry a duller green, often with blackish edges to leaves.

Morphology Stem

Stems pubescent, often densely so, with long spreading to antrorse hairs Stems pubescent, often densely so, with long spreading to antrorse hairs, or densely pubescent with long spreading to appressed silky hairs, the surface ± obscured

Distribution

Zambia, Zimbabwe, Malawi, Mozambique. Also in Tanzania.

Ecology

In miombo or Terminalia–Combretum woodland and grassland; 900–1500 m.

Conservation

Widespread; Least Concern.

Extinction risk predictions for the world's flowering plants to support their conservation (2024). Bachman, S.P., Brown, M.J.M., Leão, T.C.C., Lughadha, E.N., Walker, B.E. https://nph.onlinelibrary.wiley.com/doi/full/10.1111/nph.19592

Conservation

Predicted extinction risk: not threatened. Confidence: confident