6 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 
A small but very interesting collection of herbarium specimens 
made by Doctor MacDougal forms the basis of this paper. No 
attempt was made to obtain a full representation of the flora of the 
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Fic. 1.—Map of the Sonoran Desert Region between Tucson, Arizona, and the Gulf of California. 
region but only those plants were taken which were especially inter- 
esting or were in suitable condition. In addition a large series of 
photographs showing the botanical and geographical features was 
