Hygrophila auriculata (Schumach.) Heine

IUCN Red List of Threatened Species https://www.iucnredlist.org/species/168863/120119714

Conservation

LC - least concern

Acanthaceae, H. Heine. Flora of West Tropical Africa 2. 1963

Morphology General Habit

A stout erect herb of wet places, 2-3 ft. or up to 6 ft. or more

Morphology Stem

4-angled usually bristly stem,

Morphology Reproductive morphology Flowers

Bluish or purple flowers 1-1 1/4 in. long in dense whorls with about 6 strong spines.

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

Type

“India”, Hortus Malabaricus 2: t.87, fig.45 (1679).

Morphology General Habit

Erect usually unbranched annual herb, rarely with basal part of stem creeping and rooting; stems up to 100 cm long, quadrangular to rounded, sparsely to densely hirsute-strigose upwards with broad glossy hairs, usually with puberulent indumentum underneath, rarely subglabrous

Morphology Leaves

Leaves subglabrous to hirsute-strigose with glossy white hairs; lamina lanceolate to narrowly ovate or narrowly elliptic, largest 7–23 × 0.3–2.3 cm; apex subacute to acuminate; base attenuate to subcordate, rarely hastate

Morphology Reproductive morphology Flowers

Flowers in dense sessile many-flowered axillary fascicles on upper part of stem, each with 6 hard yellowish to brownish spines (modified branches) to 3(4) cm long; bracts numerous, becoming hard and ± bony in basal part, lanceolate to narrowly elliptic, up to 5 cm long, hirsute-strigose in basal part, puberulent and ciliate apically

Morphology Reproductive morphology Flowers Calyx

Calyx 8–20 mm long, hirsute-strigose apically and along midribs, lobes all strongly ribbed, ventral pair fused almost to apex, others for 2–3 mm at base, ventral and lateral linear-lanceolate, dorsal 1–5 mm longer and lanceolate to oblanceolate

Morphology Reproductive morphology Flowers Corolla

Corolla white or pale mauve, pale lilac, blue or purple, rugula conspicuous, white with reddish veins, 22–39 mm long of which linear tube 8–14 mm and expanded tube plus limb 13–26 mm, puberulent or sparsely so and usually with capitate glands; dorsal lip ovate to elliptic, lobes 2–5 mm long, rounded; ventral lip with few to many long tapering hairs, broadly obovate, lobes 4–7 mm long, rounded or emarginate, all same width

Morphology Reproductive morphology Flowers Androecium Stamens Filaments

Filaments glabrous or with a few short stubby hairs near base, dorsal 4–10 mm long, ventral 7–14 mm; anthers 2–3 mm long; stigmatic lobe 1–2 mm long

Morphology Reproductive morphology Fruits

Capsule enclosed in hardened basal part of bracts, retained on plant, glabrous, 7–12 mm long, with 2–6 seeds per locule

Morphology Reproductive morphology Seeds

Seeds 1.5–2 mm long.

Distribution

Zambia, Zimbabwe, Malawi, Mozambique. Widespread in tropical Africa and in India.

Ecology

Seasonally flooded grassland, usually on clay, alluvial woodland and bushland, riverbanks and riverbeds, often forming large stands; 0–1500 m.

Conservation

Widespread; not threatened.

Recognition

In the Flora area Hygrophila schulli differs from the rest of the genus in the hardened spines which surround the inflorescences. These are modified branches, as can be seen from the scars or even minute leaves which often appear. It also differs in having the two ventral sepals fused and in the hardened basal part of the bracts which retain the capsule on the plant. The number of ovules (2–6) is also unusually low in the genus as are the relatively large seeds. It may be that further work will show that Asteracantha can be resurrected. This is the most widespread species in the genus and the most variable, but there appears to be no way of subdividing the bewildering array of material. Several different forms (e.g. white flowered or mauve flowered, subglabrous or densely hairy) can often be found together in the same locality with few or no intermediates, but in the next a different pattern is found. The typical form with hastate leaf-base is rare in the Flora area and has only been seen in N Zambia.

IUCN Red List of Threatened Species https://www.iucnredlist.org/species/177163/84286810

Conservation

LC - least concern

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

Morphology Reproductive morphology Flowers

Flowers in dense sessile many-flowered fascicles in the upper part of the stem, each with up to 6 hard yellowish to brownish finely puberulous spines (modified branches) up to 5 cm long (rarely absent); bracts numerous, becoming hard and ± bony in basal part, lanceolate to ovate or elliptic, up to 5(–7) cm long, finely puberulous and ciliate or hirsute-strigose in basal part

Morphology Reproductive morphology Flowers Calyx

Calyx finely puberulous or hirsute-strigose apically and along midribs, 12–25(–30) mm long; lobes all strongly ribbed, ventral pair fused almost to apex, the others for 2–3 mm at base, ventral and lateral linear-lanceolate, dorsal 1–6 mm longer and lanceolate to oblanceolate

Morphology Reproductive morphology Flowers Corolla

Corolla white or pale mauve, pale lilac, blue or purple, “herring-bones” conspicuous, white with reddish to purplish veins, finely puberulous or sparsely so and usually with capitate glands, 22–40 mm long of which linear tube 8–14 mm and expanded tube plus limb 13–27 mm; upper lip ovate to elliptic, lobes 2–5 mm long, rounded; lower lip with few to many long tapering hairs, broadly obovate, lobes 4–8 mm long, rounded

Morphology Reproductive morphology Flowers Androecium Stamens Filaments

Filaments glabrous or with a few short stubby hairs near base, upper 4–10 mm long, lower 7–14 mm; anthers 2–3 mm long

Morphology Reproductive morphology Flowers Gynoecium Stigma

Stigmatic lobe 1–2 mm long

Morphology Reproductive morphology Fruits

Capsule enclosed in the hardened basal part of the bracts, retained on plant, glabrous, 8–14 mm long, with 2–6 seeds per locule

Morphology Reproductive morphology Seeds

Seeds all 1.5–2 mm long or with 2 large seeds 3–4 mm long and 2 small seeds ± 2 mm long.

Figures

Fig 27, p177

Ecology

Seasonally flooded grassland, usually on clay soils, but occasionally on wet sand, alluvial Acacia woodland and bushland, riverbanks, riverbeds, old ricefields; near sea level to 1650 m

Note

It is quite possible that a future detailed study also including the Indian material will allow these two forms to be separated, most probably as subspecies. But at the moment I have decided to keep all the material under one broad species as there is a number of what seems to be intermediates, and – in India and West Africa – a fair number of specimens tending towards the taxon endemic to the other part of the world. Material from Uganda, W Kenya and W Tanzania ( H. auriculata, sensu stricto) has hastate auriculate leaf bases at least on the upper part of the stem, while material from the rest of the Flora area ( H. spinosa, sensu stricto) has attenuate to cuneate leaf bases. The western plants also tend to be taller and stouter. H. schulli and richardsiae differ from the rest of the species in the hardened spines which surround the inflorescences. These are modified branches as can be seen from the scars or even minute leaves which often appear. It also differs in having the two lower sepals fused, and in the hardened basal part of the bracts which retain the capsules on the plant. The number of ovules (2–6) is also unusually low in the genus as are the relatively large seeds. It may be that further work will show that Asteracantha can be resurrected. In central and east Tanzania other patterns of variation are seen. Several different forms (e.g. white flowered and mauve flowered or subglabrous or densely hairy) can often be found together in the same mbuga with few or no intermediates. But in the next mbuga a different pattern is usually found.

Type

Type: “India”, Hortus Malabaricus 2: Pl. 87, fig. 45

Morphology General Habit

Erect unbranched or branched annual herb, occasionally with basal part of stem creeping and rooting; stems up to 1.3(–1.8) m long, quadrangular to rounded, glabrous to densely hirsute-strigose upwards with broad glossy hairs, and usually with finely puberulous indumentum underneath

Morphology Leaves

Leaves linear-lanceolate to narrowly ovate or narrowly elliptic (rarely elliptic), largest 7–32 × 0.3–3(–4.2) cm, apex subacute to acuminate, base attenuate to hastate and auriculate, glabrous to hirsute-strigose with glossy white hairs

Distribution

Range: Widespread in tropical Africa and in India Flora districts: T1 T2 T3 T4 K1 K3 K4 K5 K 7 T1 T2 T3 T4 T5 T6 T7 T8 Z P