Monographs Details: Mitracarpus portoricensis (Urb.) Urb.
Authority: Britton, Nathaniel L. Flora Borinqueña.
Description:Species Description - The profuse, round balls of small, white flowers make this low shrub conspicuous and attractive. It is endemic in Porto Rico, growing abundantly in the white sands of the northern coastal plain, and has also been observed in the western mountains; nearest relative appears to be Mitracarpus frigidus native of Venezuela, and, when first made known to botanists, it was supposed to be a variety of that species, but this classification was subsequently abandoned. We have not ascertained any popular Spanish or English names for this shrub.
Mitracarpus (Greek, referring to the characteristic fruit) is a genus of thirty or more species of herbs and shrubs, most of them natives of tropical America, four species inhabiting Porto Rico. Their stems and branches are, for the most part, 4-angled, the leaves opposite, narrow or broad, with a stipular sheath bearing several bristles. The flowers are borne in dense, round clusters; the calyx is 4-toothed or 5-toothed, the lateral teeth awl-shaped, the others much smaller; the salverform or funnelform corolla has a spreading, 4-lobed limb, the lobes not overlapping; there are 4 stamens, alternate with the corolla-lobes; the usually 2-celled ovary has but 1 ovule in each cavity. The fruit is a little capsule, which opens horizontally when ripe, the top falling off like a lid, releasing the 2, round or oblong seeds, in addition to the species here illustrated, 3 others grow in Porto Rico.
Mitracarpus portoricensis is a smooth, bushy-branched shrub, from 0.3 to 0.6 meters high. Its narrow leaves are mostly clustered at the nodes of the branches, stalkless, pointed, from 3 to 6 centimeters long, and from 1 to 3 millimeters wide; the stipular sheath is about 4 millimeters long, its bristles about as long. The globose heads of flowers are mostly borne at the ends of branches and are from 1 to 2 centimeters in diameter; the lateral calyx-teeth are 2 or 3 millimeters long; the bright white corolla is about 5 millimeters long, with lobes shorter than the tube. The capsule is about 1 millimeter long.
Mitracarpus portoricensis Urban, Symbolae Antillanae 4: 600. 1911.