Monographs Details: Peiranisia polyphylla (Jacq.) Britton & Rose ex Britton & P.Wilson
Authority: Britton, Nathaniel L. Flora Borinqueña.
Description:Species Description - Southwestern Porto Rico is well worth a visit while this shrub is in full bloom in the winter or early spring, for its elegant, abundant, golden-yellow flowers then give conspicuous color to the country over large areas, and it is often planted in gardens for ornament; it blooms, less abundantly, at other times in the year. While most plentiful from Guayama westward near the southern coast, it also grows sparingly at middle elevations further inland; elsewhere it is known from the Virgin Islands and Santo Domingo.
Peiranisia (derivation not explained) is a genus proposed by the botanist Rafinesque in 1838, separated from Cassia by features of flowers, fruit and leaves; it consists of about 50 species, all natives of tropical and subtropical America; only the one here illustrated grows in Porto Rico. They are shrubs and trees, with once compound leaves, which almost always bear a gland on the stalk, and have several or many pairs of usually small leaflets. The yellow flowers are slender-stalked, solitary or in small clusters, with 5 sepals, and the 5 broad petals are all nearly alike; the perfect stamens are usually 7, their anthers opening by a terminal pore, and usually accompanied by 3 imperfect, smaller stamens (staminodes); the 1-celled ovary contains several or many ovules. The flat and narrow pods are elongated and split longitudinally along both margins, the 2 valves usually impressed between the seeds, papery in texture.
Peiranisia polyphylla (many leaves) is usually a shrub from 1 to 3 meters high, but occasionally forms a small tree about 4 meters high, its branches slender, its twigs sparingly hairy; it has been recorded as becoming much larger. The leaves are short-stalked, from 2 to 6 centimeters long, more or less clustered, and have from 5 to 15 pairs of oblong or obovate leaflets from 4 to 10 millimeters long, which are blunt, notched, or minutely tipped, somewhat hairy when young, becoming smooth, usually with an oblong gland between the lowest pair; the very narrow stipules are only 2 or 3 millimeters long; the flowers are borne among the leaves on slender stalks, solitary, or 2 together, showy, often very numerous; the oval, blunt sepals are somewhat unequal in length; the petals are broadest above the middle, about 1.5 centimeters long. The pods are nearly straight, short-stalked, from 8 to 15 centimeters long, 6 to 8 millimeters wide, shining, nearly black when ripe, the seeds flattened.
Cassia polyphylla Jacquin, Collectanea 4: 104. 1790.
Peiranisia polyphylla Britton & Rose; Britton & Wilson, Scientific Survey of Porto Rico & Virgin Islands 5:373.1924.