Parkinsonia aculeata L.
Britton, Nathaniel L. Flora Borinqueña.
Species Description - John Parkinson, commemorated by Linnaeus in this highly specialized tree, elegant through its profuse, showy, clustered, yellow flowers, was an English botanist and herbalist to King James the First; he lived from 1567 to 1650, and published in 1629 a monumental folio volume entitled "Paradisus in Sole Paradisus Terrestris", now exceedingly rare, but reprinted in London in 1904; in it he described plants of "The Garden of Pleasant Flowers" of "The Kitchen Garden" and of "The Orchard", dedicated it to the Queen, "praying that your Highnesse may enjoy the heavenly Paradise, after the many yeares fruition of this earthly;" paradisus is Latin for park. One genus is regarded as monotypic, although several other plants have been referred to it by authors, now considered as better classified in different genera. This tree or shrub inhabits dry regions, and is widely distributed nearly throughout those of tropical and subtropical America, ranging from the southern United States to Peru and Argentina, and introduced into the Old World; in Porto Rico it is locally plentiful and conspicuous in the southern and eastern districts, mostly near the coasts, but ascends the valley of the Coamo River nearly to Coamo Springs, and grows also on Vieques Island, Horse bean is another English name. It is sometimes planted for ornament. Parkinsonia aculeata (prickly) may form a small tree from 6 to 9 meters high, but is usually lower, and often shrubby, its brown bark slightly broken into small plates, the slender, spiny branches spreading, or drooping, the young twigs hairy, the spines about 3 centimeters long, or shorter. The very peculiar leaves are nearly stalkless, twice compound, but with a very short, spine-tipped axis (rachis) bearing 1 or 2 pairs of slender, greatly elongated divisions 20 to 40 centimeters long, which appear like stalkless, once-compound leaves; these are flattened, narrowly winged, and bear from 10 to 55 pairs of linear to obovate leaflets, only about 8 millimeters long, or shorter, or sometimes are without leaflets. The flowers are few or several in loose clusters shorter than the leaves, or as long, their slender stalks from 5 to 20 millimeters long; the calyx has a short tube and 5, narrow segments about 7 millimeters long; the 5 spreading petals are all nearly alike, nearly orbicular, about twice as long as the calyx; the 10, separate stamens are about one-half as long as the petals, their filaments woolly at the base, their anthers attached near the middle; the ovary is short-stalked and contains many ovules, the style very slender, topped by a small stigma. The pods are slender-cylindric, leathery, drooping, from 5 to 15 centimeters long, characteristically deeply constricted between the seeds and striate-veined; the oblong seeds about a centimeter long.
Palo de rayo Jerusalem Thorn Senna Family Parkinsonia aculeata Linneaus, Species plantarum 375. 1755.