Common names: MILKVETCH, LOCOWEED, RATTLEWEED, WOOLLY-LOCO Arizona and California deserts: (_Astragalus nuttalianus_). White-purple. February-May. Texas deserts: (_Astragalus mollissimus_). Purple. April-May. Pea family. Size: 4 to 12 inches high. A very large genus of plants, with 78 species recorded in Arizona alone, _Astragalus_ ranges from the driest, hottest parts of the desert to high mountain peaks and the far north. _A. nuttalianus_ is the commonest of the desert species and is found on dry plains, mesas, and slopes below 4,000 feet from Arkansas and Texas westward to California and south into Mexico. Some of the species, of which _Mollisimus_ (Wooly-loco) is one, contain a poisonous constituent causing the well-known and often fatal loco disease of livestock, particularly horses. (Loco is a Spanish word meaning “crazy.”) Other species which prefer soils rich in selenium take up enough of that toxic mineral to make them poisonous to livestock, especially sheep. Nearly all of the species are colorful and spectacular when in blossom, and some of them have a rank, disagreeable odor. PURPLE [Illustration: Solanum elaeagnifolium S. rostratum] Common names: PURPLE NIGHTSHADE, GROUNDCHERRY, WILD POTATO, (_TROMPILLO_), HORSENETTLE Arizona and California deserts: (_Solanum xanti_). Purple. April-August. Texas desert: (_Solanum elaeagnifolium_). Purple-violet. May-September. Potato family. Size: Up to 3 feet. Quite showy when in flower, these common roadside plants attract considerable attention during the late spring and summer. Some species become troublesome in cultivated fields and are difficult to eradicate. An alkaloid, solanin, reported as present in the leaves and unripe fruits of several species, renders them poisonous. Pima Indians add the crushed berries of _S. elaeagnofolium_ to milk in making cheese. The yellow-flowered _S. rostratum_ is heavily covered with spines, including both stems and fruit, giving it the name of Buffalobur. This species is said to be the original host of the now widespread pest, the Colorado Potato Beetle. PURPLE [Illustration: Heliotropium curassavicum] Common names: WILD-HELIOTROPE, QUAILPLANT, CHINESE-PUSLEY Arizona, California and Texas deserts: (_Heliotropium curassavicum_). Purple. March-April. Borage family. Size: Spreading, weak stems up to 18 inches.