Hygrophila abyssinica (Hochst. ex Nees) T.Anderson

J. R. Timberlake, E. S. Martins (2013). Flora Zambesiaca, Vol 8 (5) Acanthaceae Part 1. Royal Botanic Gardens, Kew

Type

Sudan, Sennar, 1837–1838, Kotschy 293 (K lectotype, BM), selected here (other syntype collected by Schimper in Ethiopia).

Morphology General Habit

Annual or short-lived perennial herb, sometimes viscid, said to smell like catmint when crushed, sometimes aquatic with emergent flowering stems or wholly submerged; stems suberect, ascending or procumbent, up to 50(75) cm long, rounded to quadrangular, glabrous to puberulous and ± long pilose hairs and ± capitate glands

Morphology Leaves

Leaves glabrous to puberulous, ± longer hairs and capitate glands; lamina narrowly ovate to ovate or narrowly elliptic to elliptic, rarely lanceolate in submerged forms, largest (0.8)1.2–5.5(8) × 0.4–1.6(2) cm; apex rounded to acute, rarely acuminate; base attenuate to cuneate; margin entire to crenate-dentate with large triangular teeth

Morphology Reproductive morphology Inflorescences

Inflorescence spiciform to paniculate, to 30 cm long, interrupted or confluent into a single apical ‘head’; axis puberulous or sparsely so, often with capitate glands and longer hairs; flowers in 1–15-flowered cymes, sessile or with peduncle to 2.5 cm long; bracts to 1 cm long, glabrous to puberulous, ± capitate glands, with longer white hairs on edges; pedicels to 1 mm long

Morphology Reproductive morphology Flowers Calyx

Calyx 3–7 mm long of which fused basal part is c.1 mm, puberulous or sparsely so, with capitate glands, usually with longer hairs on edges; lobes all linear-lanceolate or dorsal slightly wider and oblanceolate, all same length or dorsal to 1 mm longer

Morphology Reproductive morphology Flowers Corolla

Corolla subactinomorphic, pale mauve or pale blue to deep blue or purplish with white or yellow throat, rarely pure white, no rugula, no orange spots, 4–8(10) mm long of which elliptic lobes 1–3 mm; tube linear with a constriction ± 1/3 above base and slightly widened upwards; puberulent, occasionally with capitate glands

Morphology Reproductive morphology Flowers Androecium Stamens

Stamens inserted just above constriction, included in tube; filaments 0.5–1 mm long, glabrous; anthers 0.5–1 mm long; style c.1 mm long, hairy, both stigmatic lobes equally developed, flattened

Morphology Reproductive morphology Fruits

Capsule puberulent, a few glands near apex, 4–7 mm long, with 8–10 seeds per locule

Morphology Reproductive morphology Seeds

Seeds c.0.5 mm long.

Distribution

Caprivi, Botswana, Zambia, Zimbabwe, Malawi, Mozambique. Also in Ghana, Nigeria, Cameroon, Central African Republic, Chad, Sudan, Ethiopia, Congo, Tanzania, Angola and Namibia.

Ecology

Riverbanks and riverbeds, swampy grassland, rheophytic in rocky riverbeds and rapids, or an aquatic in shallow rivers and lakes; 650–1750 m.

Conservation

Widespread; not threatened.

Recognition

It differs from all other species in the Flora area in the usually toothed leaves, the subactinomorphic corolla with included subsessile stamens, and the short stigma with both stigmatic lobes equally developed and flattened.

IUCN Red List of Threatened Species https://www.iucnredlist.org/species/185534/120119505

Conservation

LC - least concern

Acanthaceae (part 2), Kaj Vollesen. Flora of Tropical East Africa. 2008

Type

Types: Sudan, Sennar, Kotschy 293 (BM!, K!, isosyn.); Ethiopia, Schimper s.n. (not seen)

Morphology General Habit

Annual or short-lived perennial herb, sometimes viscid, said to smell like catmint when crushed; stems suberect, ascending or procumbent, up to 50(–75) cm long, rounded to quadrangular, glabrous to puberulous

Morphology Leaves

Leaves narrowly ovate to ovate or narrowly elliptic to elliptic, largest (0.8–)1.2–5.5(–8) × 0.4–1.6(–2) cm, apex rounded to acute (rarely acuminate), base attenuate to cuneate, margin entire to crenate-dentate with large triangular teeth, glabrous to puberulous

Morphology Reproductive morphology Inflorescences

Inflorescence spiciform to paniculate, interrupted basally, confluent apically, up to 30 cm long; axes finely puberulous, also with capitate glands and longer hairs; flowers in 1–12flowered cymes, these sessile or with peduncle up to 5 mm long; bracts up to 1 cm long, glabrous to puberulous, ± capitate glands and with longer white hairs on edges; pedicels up to 1 mm long

Morphology Reproductive morphology Flowers Calyx

Calyx finely puberulous, also with capitate glands and with longer hairs on edges, 3–7 mm long of which fused basal part ± 1 mm; lobes all linear-lanceolate or dorsal slightly wider and oblanceolate, all same length or dorsal up to 1 mm longer

Morphology Reproductive morphology Flowers Corolla

Corolla subactinomorphic, pale mauve or pale blue to deep blue or purplish with white or yellow throat (rarely pure white), no orange spots, no long stiff hairs and no “herring-bones”, finely puberulous and occasionally with capitate glands, 4–8(–10) mm long of which the elliptic lobes 1–3 mm; tube linear with a constriction about 1/3 above base and slightly widened upwards; stamens 4, didynamous, inserted just above constriction, included in tube; filaments 0.5–1 mm long, glabrous; anthers 0.5–1 mm long

Morphology Reproductive morphology Flowers Gynoecium Style

Style ± 1 mm long, hairy, both stigmatic lobes equally developed, flattened

Morphology Reproductive morphology Fruits

Capsule finely puberulous, ± a few glands near apex, 4–7 mm long, with 8–10 seeds per locule

Morphology Reproductive morphology Seeds

Seed ± 0.5 mm long

Ecology

Seepage area in Brachystegia woodland, riverbanks, sandy soil; ± 275 m

Note

H. abyssinica differs from all other species in the usually toothed leaves, the subactinomorphic corolla without long stiff hairs but with included subsessile stamens and in the short stigma with both stigmatic lobes equally developed and flattened. An extremely variable species as can be guessed from the lengthy synonymy. But on closer examination the variation is only in growth form and vigour. Calyx, corolla, fruit and seeds are constant throughout, and I have been unable to separate out any infraspecific taxa despite its large distribution and large disjunction from northern to southern Africa. Of the three collections cited as types for Hemigraphis schweinfurthii the other two ( Schweinfurth 2708 and 2764) are Hygrophila africana (T.Anderson) Heine. Heine in Adansonia 11: 657 (1971) erroneously cites Schweinfurth 2708 as H. abyssinica. H. abyssinica is very close to the Indian H. polysperma (Roxb.) T.Anders. which differs mainly in having two fertile stamens plus two staminodes. It is quite possible that a thorough study will reveal that the two are at most subspecifically distinct. See also note after H. linearis.

Distribution

Range: Ghana, Nigeria, Cameroon, Central African Republic, Chad, Congo-Kinshasa, Sudan, Ethiopia, Angola, Zambia, Malawi, Mozambique, Zimbabwe, Botswana, Namibia Flora districts: T6

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