DEPARTMENT OP BOTANICAl, RESEARCH. 65 



negiea gigantea was especially conspicuous, and its southern geographical 

 limits were more definitely fixed than heretofore. This species was traced 

 as far south as the Yaqui River in southern Sonora. Pachycereus pringlei, 

 another of these giant cacti, was very common about Guaymas, which seems 

 to be near the southern limit of the species. The most striking and by far 

 the most abundant of these giant cacti is Pachycereus pecten-aboriginum, 

 which was observed from Guaymas to Acaponeta, a distance of about 500 

 miles, extending in a broad band 100 miles broad east and west. Lemareo- 

 cereus thurberi extends from southern Arizona as far south as Culiacan. 

 South of Guaymas this species is very abundant and assumes much larger 

 dimensions than in its northern range. 



Four species of giant Bchinocactiis, usually called visnaga or barrel cactus, 

 were observed on the trip. Several of the species are extensively used in 

 making a Mexican candy. Numerous species of Opuntia, Mamillaria, and 

 Cereus were collected and studied in the field. 



MISCELLANEOUS. 



The facilities of the Desert Laboratory were granted to Dr. W. H. Brown, 

 research fellow of Johns Hopkins University, in September 1910, for one 

 year, for the purpose of carrying on some work on problems in soil-moisture 

 and transpiration. 



Mr. J. G. Brown, Associate Professor in Botany of the University of Ari- 

 zona, has carried on some work on morphology of cacti at the Desert Labora- 

 tory since January 191 o, and has also given some assistance in other work 

 in progress. 



Prof. F. E. Lloyd, of the Alabama Polytechnic Institute, was in residence 

 at the Desert Laboratory in August 1910, during which time he reinvestigated 

 certain features of stomatal movement and associated phenomena in Verbena, 

 and extended his observations to Amaranthus. The results earlier published 

 on Verbena (Publication No. 82) were confirmed. Stomatal movement and 

 relative transpiration, water content (a) of the plant as a whole and (b) of 

 the leaves, and absolute transpiration in the Ocotillo (Fouqiiieria splendens) 

 were studied. Important correlations between fluctuation in transpiration 

 rate and in water content were observed, bringing to light the necessity of 

 further investigation of the relation between the income and outgo of water 

 in the plants. 



EQUIPMENT. 



A number of pieces of apparatus of conventional types have been added 

 to the equipment at Tucson and Carmel. A small plot of ground adjacent 

 to the laboratory at Carmel has been purchased for experiments with cacti, 

 while the cultures of species from high mountain habitats are installed in a 

 leased garden tract. 



The field-work in connection with Dr. Huntington's investigations upon 

 desert climatic conditions involving some extended travel, a 30 horse-power 

 motor with detachable tonneau was purchased and equipped with 34 x 4}^ 



5— YB 



