Idria and FouquieriaC are the only genera of the Fouquieriaceae, a family confined to southwestern North America. Fouqtieria consists of eight recognized species, of which one, F. splendcns Engelm., is comparatively well known. It has the widest range of any member of the family, occurring in the United States in southern California, extreme southern Nevada, the southern halves of Arizona and New Mexico, and the southwestern corner of Texas. On the mainland of Mexico its range is imperfectly known, but it is found as far south as the 26th parallel. In Lower California it occurs at least as far south as a point just north of the 28th parallel (Shreve, I93I). The other species of Foitquiieria. are limited in their distribution to Mexico, and are little known (Shreve, I93I). Idria contains a single species (I. columnaris Kellog) which is found in Lower California from about the 30th parallel of latitude on the north to, 27' 6o' on the south, a distance in this direction of approximately 200 miles. From east to west it occurs across the peninsula, and may be expected wherever granite rock is encountered. Idria is also known from a small area on the coast of Sonora, just south of the 3oth parallel (Shreve, I93I). These plants are of interest in several ways. Their taxonomic position has always been a matter of dispute, and it is possible that their present classification is incorrect. In this connection cytological studies might prove of great value. The bizarre appearance of the plants Fouquieria with its branches radiating upward and outward from the base, each of these topped in spring by a flame-colored inflorescence, and Idria with its thick, almost prehistoric-appearing trunk that looks not unlike a greatly elongated inverted parsnip has drawn comment from naturalists from the time of their discovery. Both Idria (locally known as ) and Fouquieria (popularly called the ocotillo or candle bush) have become modified along very definite lines in response to their arid habitat. The cirio is decidedly a stem succulent, while the ocotillo, although possessing a rather thick cortex on both stem and roots, is rather of a woody type. It has developed to a remarkable degree, however, the faculty of dispensing with its leaves as a response to water shortage. The same feature is present in [dria, though to a lesser extent, perhaps because of the greater amount of reserve water stored in the