56 



BOTANICAL GAZETTE 



[JULY 



turn, Yucca, Agave, and Opuntia. So far as might be estimated by 

 the instruments at hand, the mountain is probably the one on the 

 hydrographic map of 1873-75 designated as a "sharp white peak 

 4288 ft ," which had not previously been ascended, and still bears no 

 name. 



METEOROLOGICAL FEATURES. 



Data bearing on the climatic conditions in the delta and of the 

 contiguous deserts are very meager. Records have been kept at 

 Yuma for a long term of years, and some data obtained at Torres, 

 Sonora, quoted in the recent contribution by Mr. Coville and the 

 author, 11 constitute the only information available. The following 

 table taken from the records of the U. S. Weather Bureau 12 gives 

 the conditions at the head of the delta. 



The transcript of the record was furnished by Hon. Willis L. Moore 

 Chief U. S. Weather Bureau. 



MEAN RELATIVE HUMIDITY. 



8 A. M. 



8 P. M. 



1903. 

 1904. 



28.0 



20.7 



44.8 



21. 7 



23.0 



17.0 



17.9 



17.8 



21.7 



2.82 



30.9 



237 



28.4 



24.2 



It is to be seen that the delta and the contiguous districts have an 

 annual precipitation of less than 7 cm , and that less than 2 cm was 



" Desert Botanical Laboratory of the Carnegie Institution, p. 23. November 1903. 



I* Greely and Glasford, Report on the climate of Arizona. Ex. Doc. No. 2S7. 

 Washington. 189 1. Climate and Crop service, U. S. Weather Bureau. Report for 

 Arizona Sec tion for 1903. 



