554 
CVI. ACANTHACE^. 
Order CVI. ACANTHACE^E 
Herbs, shrubs or twiners, rarely lianes ( Thunbergia ). Leaves 
opposite, often unequal, in some Polytremas alternate. Flowers 
often showy strobilate spikes, heads or cymes, bisexual, irregular. 
Calyx inferior at base; lobes 5 or 4, nearly free to base. 
Corolla gamopetalous, tube campanulate or cylindric, limb 
2-lipped or 5-lobed. Stamens 4, didynamous or 2, anther-cells 
2 or 1. Pollen ellipsoid and ribbed or globose, honeycombed or 
spiny. Ovary superior, 2-celled. Ovules 2 or 1 or several, super¬ 
imposed in vertical rows (or 2 collateral, Thunbergia). Style long, 
bifid at top. Capsule loculicidal, often elastically dehiscent. 
Seeds usually as many as ovules, held up on retinacula, curved stiff 
outgrowths of the funicle by which they are ejected from the 
capsule. Species 2000, tropics and sub-tropics. (Clarke, Journ. 
^fs. Soc. Beng. Ixxiv. 628.) 
Twiners, with, 3 or 2 seeds in capsule. 
Herbs; seeds 8 to 16 in 2 rows in capsule; no 
retinacula. 
r. 
Thunbergia 
Stamens 2 ...... 
2. 
Nelsonia 
Stamens 4 ...... 
Retinacula present. 
Capsule with more than 4 seeds hygroscopically 
shaggy on edge. 
3 - 
Staurogyne 
Capsule clavate. Pollen honeycombed 
Capsule seed-bearing from base. Pollen 
4 - 
Ruellia 
spiny ...... 
Capsule hardly stalked. Pollen ellipsoid, 
ribbed. 
Corolla distinctly 2-lipped. 
5 - 
Aporuellia 
Spikes in continuous or axillary clusters. 
6. 
Hygrophila 
Flowers in 1 -sided axillary racemes 
Corolla hardly 2-lipped. 
7 - 
Nomaphila 
Panicle thyroid, hardly 1 ft. long . 
Spikes terminal or axillary, dense with 
8. 
Stenothyrsus 
distinct bracts .... 
Capsule with 4 or 2 seeds. Corolla indistinctly 
2-lipped; shrubby herbs or bushes. 
Pollen ellipsoid, ribbed. 
9 - 
Hemigraphis 
Stamens 2 ..... 
10. 
Endopogon 
Stamens 4 ..... 
11. 
Strobilanthes 
Pollen globose, spiny; stamens 4 
12. 
Acanthopale 
Corolla with upper lip small, lower 3-lobed, 
midlobe bifid; spiny-leaved, tidal 
mud herbs . . . . 13. Acanthus 
Corolla 2-lipped, lobes imbricate in bud; 
retinacula present. 
Capsule with more than 4 seeds ; stamens 2. 
Capsule cylindric solid at base; seeds in 
globose top . . . . -14. Phlogacanthus 
Capsule with parallel sides seed bearing from 
base; corolla-tube cylindric. 
Seeds hairy on edge; flowers in long spikes 15. Gymnostachyum 
Seeds glabrous, much-branched herbs; 
flowers distant . . . .16. Andrographis 
