128 REPORTS ON INVESTIGATIONS AND PROJECTS. 



which He in a zone in which the annual precipitation does not exceed ten 

 inches. The vegetation is composed chiefly of compositaceous types with 

 reduced surfaces fitted for conserving rather than storing moisture and of 

 chenopodiaceous forms, such as are characteristic of regions with soils 

 highly charged v/ith salts. 



The latter part of August and the month of September were spent in 

 making an examination of the desert conditions, and the general aspect of 

 the vegetation near Laredo, Texas ; Saltillo, Mexico City, and in the region 

 southward from Tehuacan to Mitla, in latitude 17° N. By the cooperation 

 of Dr. J. N. Rose, assistant curator of botany in the Smithsonian Institution, 

 detailed studies were made which would have been impossible without its 

 aid. The Tehuacan desert was found to constitute a type not hitherto exam- 

 ined, and to be extremely rich in plants with adaptations for the storage of 

 water. Among these are the numerous massive cacti, several genera of 

 which are represented by species that surpass the saguaro of Arizona in bulk. 

 Three species of Bcaucarnea were encountered in which the storage function 

 is highly developed, and one of these, Beaucarnca oedipns, probably has a 

 capacity for holding as much as a ton, or even a ton and a half, of water in 

 reserve for its needs during dry periods. Much valuable living material was 

 secured and sent to the Desert Laboratory for experimental purposes, and a 

 carload of succulents was shipped to New York to be used by Drs. Britton 

 and Rose in their investigations of the Cactacese. 



Numerous expeditions, participated in by the various members of the 

 staff of the Desert Laboratory, have been made to the Santa Catalina Moun- 

 tains, the Sierritas, Quijotoa, and Tucson Mountains, and to several areas 

 within a radius of 100 miles from the Laboratory. These trips are always 

 organized for some special purpose, such as securing material for experi- 

 mentation, or the examination of the structure or distribution of desert 

 forms. Many of them have been shared by visiting naturalists. 



Physiology of Genetics, by Dr. D. T. MacDougal. — In continuance of some 

 investigations begun at the New York Botanical Garden in 1902 a series 

 of cultures has been carried in the New York Botanical Garden by the 

 courtesy of Dr. N. L. Britton, director, in which the assistance of Miss A. A. 

 Knox has been obtained. The series of mutants or individuals appearing 

 in the progeny of pure strains of plants which differed from the parental 

 forms by appreciable qualities, obtained by deVries in Oenothera lamarckiana, 

 have been tested and in main confirmations of his results secured. The 

 mutants did not in any case occur in a proportion greater than 5 per cent of 

 the entire progeny and were identical with the forms secured in Amsterdam, 

 with perhaps one exception. Seeds obtained from various parts of the world, 

 from some localities in which the plant has been noted since 1854, were found 

 to produce a low percentage of mutants. 



