The scientific name meaning “of the Centaurs” refers to the use by the Centaurs of certain species for healing. The cornflower or bachelor’s button (_Centaurea cyanus_) is a well-known garden annual.
[Illustration: WAVY-LEAVED THISTLE PURPLE-THISTLE]
Wavy-Leaved Thistle (_Carduus undulatus_) is the common prairie thistle and is particularly abundant in the vicinity of Fort Worth. It grows only 1-2 feet high, and the upper leaf-surfaces are yellow-green. The heads are nearly twice as large as those of the purple thistle, and the flowers are a lovely lavender color. It ranges from Southern Canada to Texas and Arizona and blooms in Texas from April to June.
Purple Thistle (_Carduus austrinus_) is the common thistle in the south-central part of the state. It is a tall, much branched plant, 3-4 feet high, with long-stalked heads of purple flowers. The stems are white-woolly, and the leaves are white-felty beneath and dark-green above, wavy-margined, lobed or divided, the segments being tipped with spines. The heads are about 1½ inches high and broad. The numerous light purple flowers are all tubular with narrow lobes. The thistles belong to a large group, its most renowned representative being the Scotch thistle.
Nodding Thistle. Silver Puffs. Sunbonnet Babies (_Thrysanthema nutans_) lacks the spines of the true thistles, but other characters show that this interesting little plant is closely related to the thistle group. The leaves form a basal rosette from which grows the slender, leafless flowering stalk bearing the nodding flower head. The lyre-shaped leaves are wavy-margined, dark-green above and white-felty below, 2-4 inches long. The stalk is sometimes 15 inches long but is commonly about 8 inches high. The creamy-white flowers are rather inconspicuous, but as the seeds mature, the soft white bristles spread into a showy whorl. The plants are found in scattered places in rich soil from Central Texas to Mexico.
Closely kin to the nodding thistle is the desert holly (_Perezia nana_), which has salmon-pink flowers and holly-like leaves. It is a low plant seeking the shelter of creosote bush, yucca, and other shrubs in West Texas.
Plants with milky juice; all flowers strap-shaped, in dense heads, surrounded by involucral bracts; corolla 5-lobed; stamens 5; ovary inferior.