Angiosperms (Flowering Plants) • Earth.com

Spiny Milkwort

(Rhinotropis subspinosa)

galery
en

Description

Rhinotropis subspinosa, synonym Polygala subspinosa, is a species of flowering plant in the milkwort family known by the common name spiny milkwort. It is native to the southwestern United States, where it grows in desert and plateau habitat. It is a perennial herb or small shrub growing in a clump no more than 25 centimeters tall. The stems have woody bases and green, thorn-tipped branches. The leaves are up to 3 centimeters in length and generally oval in shape. The flowers have winglike pairs of bright pink sepals and the keeled central petal is tipped with a yellowish beak, sometimes fringed at the tip. 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.

Taxonomic tree:

Domain:
Kingdom: Plantae
Phylum: Magnoliophyta
Class: Magnoliopsida
Order:Fabales
Family:Polygalaceae
Genus:Rhinotropis
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