Diodia rigida Cham. & Schltdl.

• Title

  Diodia rigida Cham. & Schltdl.

• Authors

  Nathaniel Lord Britton, Frances W. Horne

• Scientific Name

  Diodia rigida Cham. & Schltdl.

• Description

  Flora Borinqueña Diodia rigida Southern Buttonweed Family Rubiaceae Madder Family Diodia rigida Chamisso and Schlechtendal, Linnaea 3: 341. 1828. A low, narrow-leaved, perennial herb, with small, but pretty, axillary flowers, frequent in dry, sandy, or gravelly soil at lower elevations in Porto Rico, growing in fields, on banks and on hillsides, ascending to about 200 meters elevation. It ranges through Santo Domingo, Haiti and Cuba to Florida, grows on St Thomas, on the Dutch Islands off the Colombian coast, and has wide distribution in continental tropical America. We have found no Spanish name recorded. Diodia (Greek, thoroughfare, where some kinds grow), is a Linnaean genus of herbs, and herbaceous vines, including some 25 species, mostly American, with opposite, usually sessile, untoothed leaves, and small, axillary flowers. The obconic, or obovoid calyx has a usually 2-toothed, or 4-toothed limb; the usually 4-lobed corolla is salverform or funnelform; the usually 4 stamens are borne on the throat of the corolla, with slender filaments, and narrow anthers; the mostly 2-celled ovary has 1 ovule in each cell; the style is slender, the stigmas 2. The small, dry fruit separates into 2 carpels, each containing an oblong seed. Diodia rigida (stiff, but not remarkably) is usually branched at the base, the 4-sided branches prostrate, or ascending, from 20 to 80 centimeters long, smooth, or hairy. The short, stipular sheath of the leaves bears several bristles from 4 to 6 millimeters long. The lance-shaped, rough, sharply pointed leaves are from 1.5 to 3 centimeters long. The flowers are stalkless, and mostly solitary in the leaf-axils; the narrow calyx-teeth are about 1 millimeter long; the funnelform, rose, or white corolla is from 12 to 15 millimeters long, with pointed lobes. The nearly globular fruit is about 2.5 millimeters in diameter, smooth, or finely hairy. There are 2 other species of Diodia in the Porto Rico Flora, prostrate, or vine-like plants, with broader leaves.