The Tissues of Some of the Plants of the Soto! Region 
By WILLIAM L. BRAy 
The opening of the desert botanical laboratory of the Carnegie 
Institution at Tucson, Arizona, with its facilities for studying the 
environmental conditions and the life phenomena of desert vege- 
tation, marks an appropriate time for beginning a revival of the 
study of the tissues of desert plants. During the period of great 
activity of the study of plant structures as related to environment, 
say, from 1880 to. 1895, desert plants—at any rate xerophytic 
plants — were especially selected because of the very striking 
adaptive phenomena exhibited in their organs and tissues. The 
literature of the period abounds in noteworthy contributions to our 
knowledge of the structure of desert plants, and their means of 
adaptation to their environment, of which perhaps the most note- 
worthy was Volken’s “Flora der aegyptisch-arabischen Wiiste”’ 
(1887), although in the more general ecological works, such as 
Haberlandt’s “ Physiologische Pflanzenanatomie” (1884; ed. 2, 
1896), Warming’s ‘Lehrbuch der .dkologischen Pflanzengeo- 
graphie”” (1896; original Danish ed., 1895) and Schimper’s 
“ Pflanzen-geographie auf physiologischer Grundlage ” (1898), the 
structures of desert plants have supplied many of the most instruc- 
tive and interesting examples in adaptation phenomena. 
During this active period, the various ecological forms and the 
More numerous adaptation devices in xerophytes were described, 
so that for us there would now seem to remain little to say as to the 
effect of desert environment upon the form or habit of plants, and 
upon the structure of various tissues such as epidermal, assimilation, 
absorption, etc. Asa matter of fact, however, very few of the eco- 
logical forms of our American desert vegetation have been em- 
braced ina special physiologic-anatomical study, and besides, prog- 
tess has been made, meanwhile, in the study of physiological proc- 
€sses in plants, so that it would appear reasonable to expect helpful 
results from a renewed study of tissues of desert plants in the light 
of the most recent physiological knowledge. _If the vital phenom- 
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