Pterodiscus
(from pteron, a wing, and discus, a disk; referring to the broad wings of the disk of the fruit). ORD. Pedalineae. A genus consisting of only three species of greenhouse, herbaceous plants, with tuberous roots, or with a thick, succulent stem, which becomes tall under cultivation; two are natives of South Africa, and the third is Angolan. Flowers purple or lurid-yellow, solitary in the axils, very shortly stalked or almost sessile; calyx small, five-parted; corolla tube gibbous at base, swollen upwards; limb somewhat bilabiate, with five broadly rotundate, spreading lobes. Leaves opposite or alternate, narrow, toothed or cut, rather thick, canescent. The only species worth growing is P. speciosus. This is a handsome plant, and thrives best under the influence of a full exposure to sunlight. It requires a compost of sandy loam and leaf mould. Propagated by seeds, sown in spring and autumn; and by dividing the plant, in spring. P. luridus requires similar treatment. P. luridus (lurid). fl. dull yellow, tubular. July. l. linear-oblong, deeply lobed, almost pinnatifid. h. 1 1/2ft. South Africa, 1868. A gouty-stemmed plant, of little horticultural value. (B. M. 5784.) P. speciosus (showy).* fl. of a beautiful lilac or reddish colour, axillary, solitary, large, with a funnel-shaped tube, and a spreading, five-lobed limb. May. l. opposite, sinuate, dentate. Stem branching into several erect, thick branches. Roots large, globose, tuberous, the upper part elevated above the earth. h. 2ft. South Africa, 1848. (B. M. 4117.)