Oxypetalum
(from oxys, sharp, and petalum, a petal; petals sharp-pointed). SYNS. Gothofreda, Schizostemma, and Tweedia. ORD. Asclepiadeae. A genus comprising about fifty species of erect or twining, stove or greenhouse, perennial herbs or sub-shrubs, natives of South America, mostly Brazil, one species being found in Mexico and the West Indies. Flowers blue, white, yellowish-white, or purplish; calyx five-parted; corolla tube short, campanulate or almost globular, and with five often narrow lobes; cymes sometimes umbelliform, loosely few-flowered, sometimes capitate, rarely corymbosely branched, terminal or (in one species) axillary, pedunculate. Leaves opposite. The species mentioned below (probably the only ones introduced) like a rich, well-drained, loamy soil, and do best if planted out inside the stove or greenhouse, and their shoots trained near the glass. O. caeruleum is a charming climber, remarkable for the changes in colour exhibited by the flower at various stages of its existence. When first open, it is pale blue, with a slight tinge of green; then purplish, and, when withered, lilac. All are propagated by cuttings of the young growths, inserted under a bell glass, in bottom heat.
O. appendiculatum (appendiculate). fl. pale yellow, fragrant; petals narrow-lanceolate, acute, erectly spreading; peduncles cymose, usually four-flowered. l. ovate, acuminated, cordate, downy. Brazil, 1823. Stove twiner.
O. Banksii (Banks'). fl. purple; corolla segments linear or linear-lanceolate; peduncles lax-flowered, longer than the pedicels. June. l. cordate or ovate-cordate, shortly acuminate, incano-puberulous beneath. Brazil, 1826. Stove twining sub-shrub.
O. caeruleum (blue).* fl. blue; segments of corolla oblong, spreading; peduncles shorter than the leaves, few-flowered, erect. July. l. cordate-oblong or cordate-lanceolate, mucronate, tomentose on both sides. Buenos Ayres, 1832. Greenhouse or stove twining sub-shrub. (B. 55; B. M. 3630, under name of Tweedia versicolor; S. B. F. G. ser. ii. 407, under name of T. caerulea.) O. solanoides (Solanum-like). fl. bluish, tinged with rose-colour; corolla segments spreading; peduncles terminal or extra-axillary, corymbosely paniculate, many-flowered. June. l. lanceolate or oblong-cordate, mucronate, acute, petiolate, tomentose. Stem almost unbranched, erect. h. 6ft. Brazil, 1846. Stove sub-shrub. (B. M. 4367.)