Desert Polygala

Description

Rhinotropis acanthoclada, synonym Polygala acanthoclada, is a species of flowering plant in the milkwort family known by the common names desert polygala and thorn milkwort. It is native to the desert woodlands of the southwestern United States from Utah to the Mojave Desert. It is a small, bushy shrub spreading or growing erect and approaching one meter in maximum height. It is hairy in texture, the youngest twigs hairiest with a feltlike coat of short, whitish fibers. The lance-shaped or oval leaves are up to 2.5 centimeters long. Some of the twigs narrow to spines at the tips, especially in the inflorescences. The flowers are solitary or in clusters of up to 15. Each flower has five sepals, the lateral two white in color and spreading out like wings. The middle petal is keeled, with a flat tip protruding. The fruit is a capsule about half a centimeter long. Polygala is a large genus of flowering plants belonging to the family Polygalaceae. They are commonly known as milkworts or snakeroots. The genus is distributed widely throughout much of the world in temperate zones and the tropics. The genus name Polygala comes from the ancient Greek "much milk", as the plant was thought to increase milk yields in cattle. As traditionally circumscribed, Polygala includes annual and perennial plants, shrubs, vines, and trees. The roots often have a scent reminiscent of wintergreen. The leaf blades are generally undivided and smooth-edged, and are alternately arranged in most species. The inflorescence is a raceme or spikelike array of several flowers; the occasional species bears solitary flowers. The flower is bilateral in shape, with two large petal-like sepals on the sides, often called the "wings", and three smaller sepals behind. There are three petals in shades of reddish purple, yellow or white, which are joined at the bases. The lower of the three is the keel petal, which is "boat-shaped, cucullate (hood-like), or helmet-shaped". The keel petal may have a beak or a fringe on the tip. Stamens and style are within the curve of the keel petal. The fruit is a capsule, sometimes winged. It contains two seeds, which are usually black, hairy and tipped with a large white aril. No members of this genus are known to form nitrogen-fixing nodules.