Acanthaceae. Tribe Thunbergieae.
Thunbergia, Linn. fil.; Benth. et Hook. f. Gen. Plant. vol. ii. p. 1072.
Thunbergia alata, Boj. ex Sims in Bot. Mag. t. 2591; Fl. Cap. vol. v.
sect. i. p. 10.
Thunbergia alata is a native of tropical Africa and Natal, but has been introduced into many warm parts of the world as an ornamental creeper, and it is often called “Black-eyed Susan.� It was first described and figured in 1825 from plants raised in England from seed collected in Mauritius.
In its natural habitat the species is found as a creeper in woods, and the bright-orange corolla with a dark maroon throat gives the flower a singularly beautiful effect. The plant grows readily under cultivation, and makes a fine trellis creeper, but in colder countries it requires the protection of a glass-house.
The petioles of the mature leaves, as will be seen from the plate, are distinctly winged, but in the younger leaves they are almost terete. The stamens, as is usually the case in the family Acanthaceae, are appendaged in some way, and exhibit two forms in this species. All the anthers are tailed, but the anther of the shorter stamen, instead of having two tails, is only tailed at the base of one pollen-sac, the other pollen-sac bearing a bunch of radiating glandular hairs.
Our plate was prepared from plants grown by Dr. I. B. Pole Evans, C.M.G., at Irene, near Pretoria.
Description:—A climber. Branches terete, hirsute. Leaves opposite, petioled; petiole 2 to 5 cm. long, at first terete, with a shallow groove on the upper side, at length expanded and winged, hirsute; lamina 2·2 to 6·5 cm. long, 2 to 5·5 cm. broad, ovate, subobtuse, lobed at the base, hirsute above and beneath, with the veins depressed above, prominent beneath. Flowers[{116}] solitary, axillary. Pedicel up to 6 cm. long, terete, hirsute. Bracts two, 2·2 cm. long, 1·2 cm. broad, ovate, obtuse, distinctly keeled, hirsute, connate on one side. Calyx with many narrow linear lobes, covered with stalked glands. Corolla-tube 2 cm. long, cylindric below, and then more or less suddenly widened into a tube 6 mm. in diameter above, glabrous without and with a ring of deflexed glandular hairs at the insertion of the stamens; limb more or less oblique, with the lobes 1·5 cm. long, 1·4 cm. broad, obovate, and with the margin concave at the apex. Stamens unequal; anthers very distinctly tailed and covered on the face with long glandular hairs; the shorter anther with only 1 tail and with a tuft of glandular hairs on the other pollen sac. Style-lobes unequal; the shorter in the form of a concave saucer; the upper deeply channelled (National Herb. Pretoria, No. 2847).