Monographs Details: Petesioides yunquense (Urb.) Britton
Authority: Britton, Nathaniel L. Flora Borinqueña.
Description:Species Description - A graceful shrub, about 3 meters high, of especial interest as restricted in distribution, in so far as known, to the summit of El Yunque, Sierra de Luquillo, in eastern Porto Rico, whence it was first made known to botanists from specimens collected by the German botanist Switenis in 1885. Its small, violet, clustered flowers are attractive. Petesioides (from resemblance to Petesia another genus) was established by Jacquin in 1763, and now known to include some 20 species of West Indian trees and shrubs, with smooth foliage and flowers, the leaves of some species serrate, of others without teeth. The small, clustered flowers are dioecious, those of some bushes staminate and infertile, those of others pistillate, and producing fruit. There are 4 or 5, separate, or partly united sepals; the corolla is tubular, that of staminate flowers with 4 or 5 short lobes, that of pistillate flowers irregularly cleft; the staminate flowers have 4 or 5 stamens with short or slender filaments; the pistillate flowers have a globose, 1-celled ovary, a short, or slender style, and much reduced or imperfect stamens. The fruit is small, globose, berry-like, 1-seeded. Petesioides yunquensis (of El Yunque) has oblong to obovate, rather thick, pointed, leaves 7 to 15 centimeters long, toothed above the middle, on stalks from 5 to 8 millimeters long, clustered at the ends of twigs, or scattered. The flowers are few or several together, in clusters about 7 centimeters long, or shorter, the individual ones on slender stalks 5 to 9 millimeters long; the corolla is from 5 to 7 millimeters long. The fruit is as yet unknown. Another species of Petesioides inhabits Porto Rico.

Discussion:El Yunque Petesioides Myrsine Family Ardisia yunquensis Urban, Symbolae Antillanae 1: 383. 1899. Wallenia yunquensis Mez, in Urban, Symbolae Antillanae 2: 413. 1901. Petesioides yunquensis Britton; Britton & Wilson, Scientific Survey of Porto Rico and the Virgin Islands 6: 59. 1925.