16 
transcript of the note-books of the expedition together with a 
discussion of the broader generalizations concerning deserts and 
desert vegetation. 
concept that the arid character of a place depends upon 
the ratio existing between the actual amount of precipitation and 
the amount of water which might be evaporated from a free sur- 
face is elaborated in its aia bearings and is made the basis 
for the delimitation of dese 
Some important new ae concerning the White Sands, a 
gypsum desert in New Mexico, are given, including an analysis 
of the substratum by Dr. Wm. J. Gies. The Sonoran desert 
also yielded many new facts of interest which may not be de- 
cribed within ae limits of this brief notice. - 
A very valuable bibliographical list of . publications which 
refer to the features of xerophytic vegetation by Dr. W. A. Can- 
non is not the least interesting and practical part of the booklet. 
As a result of the inspection tour the vicinity of Tucson was 
selected as a site for the laboratory, and a commodious building 
has been erected upon a tract’of land including several hundred 
acres donated by the city of Tucson. 
Dr. Cannon, who has been appointed resident investi- 
gator, has already entered upon his duties and has one or two 
important researches already under way. In addition to the in- 
vestigations to be carried on by the organization of the labora- 
tory, facilities are also furnished for the use of visitors who may 
wish to take up related subjects. Permission has already been 
granted to three botanists to make use of tables, and other appli- 
cations are pending. In accordance with present arrangements 
botanists desirous of availing themselves of the opportunities 
offered may send their application to Mr. Frederick V. Coville, 
1836 California Avenue, Washington, D. C., r. D. T. 
MacDougal, at the New York Botanical Garden, Bronx Park, 
New York City 
D. T. MacDoveat. 
