Many of the yellow wood-sorrels are common weeds throughout the state. There are many different species. The white or pink-flowered wood-sorrel (_Oxalis acetosella_) is considered by many people as the shamrock of Ireland; but others consider white clover (_Trifolium repens_) as the true shamrock.
Dichondra-Leaved Wood-Sorrel (_Oxalis dichondraefolia_) is a low plant of Southern Texas and Mexico which has pale yellow flowers like the yellow wood-sorrels, but the leaflets differ in being rounded and entire and resemble the leaves of the dichondras (see page 101).
[Illustration: PINK MILKWORT WHITE MILKWORT PURPLE MILKWORT]
Flowers pea-shaped; sepals 5, the 2 inner larger and often petal-like; petals 3 or 5, the lower concave, often fringed; stamens 8, united, opening by apical pores; fruit a 2-celled capsule.
Pink or Bitter Milkwort (_Polygala polygama_) is a showy-flowered milkwort growing in sandy woods in East Texas. It has erect branches with slender clusters of pink flowers about ¼ in. long and horizontal branches under the soil bearing closed flowers which are self-fertilized. It blooms in Texas in April.
White Milkwort (_Polygala alba_) has densely-flowered spikes of greenish-white flowers, the buds often tinged with purple. A drug obtained from the dried root is used as an irritant. Like the closely related Seneca snake-root (_Polygala senega_), it probably contains saponin, which will dissolve the red blood-corpuscles. The roots of the latter are used in medicine to produce vomiting and as an antidote for snake-bite. The white milkwort is common on prairies and chalky slopes from Montana to Mexico from April to July.
Purple Milkwort (_Polygala puberula_) grows in the mountains of West Texas, Arizona, and Mexico. It has much larger seed capsules than the two preceding. The capsule is one of the chief features for identifying the milkworts, being 2-celled and flattened.
Flowers staminate and pistillate, often borne in an involucre; sepals sometimes reduced or absent; petals usually absent; stamens 1 to 1,000; styles free or united at base; fruit usually a 3-lobed capsule.
Bull Nettle (_Cnidoscolus texanus_), also called tread-softly, spurge-nettle, and “mala mujer” (bad woman), is a vicious plant thickly clothed with stinging hairs and bearing clusters of tubular white flowers quite similar to the tuberose in appearance and fragrance. The plants grow 2-3 ft. high. The upper flowers bear stamens, and the flowers in the lower forks of the cluster produce seeds. The seed-capsules resemble those of other members of the spurge family in being nearly ball-shaped and deeply three-lobed. The seeds are large, edible, and very palatable. The plants are very abundant in waste places and sandy soil from Texas to Arkansas and Oklahoma, blooming from late spring until fall.