DESERT REGIONS OF NORTH AMERICA. 7 
vegetation a much more rational basis will be afforded for efforts at accli- 
matization. 
A small plantation has been established in the grounds of the Labor- 
atory in the alluvial valley of the Santa Cruz River at an elevation of 
2,100 feet, with a rainfall averaging 12 inches; and a second on the slopes 
of the Santa Catalina Mountains, in an arid locality at an elevation of 
about 5,400 feet. A third series of experimental cultures has been 
installed in Marshall Gulch, on the southern slopes of Mount Lemon, the 
culminating peak of the range, at an elevation of about 8,o00 feet. The 
rainfall in the last-named locality is such that the vegetation is of a dis- 
tinctly mesophytic character. Steps are taken to obtain thermometric 
and other data which will allow an analysis of the climate in all of the 
localities named. Several years will be necessary before any definite 
conclusions may be drawn from the results of these cultures, which, 
however, already present some new and striking facts. 
DESERT REGIONS OF NORTH AMERICA. 
TRANSITION FROM THE HUMID REGIONS TO THE CHIHUAHUA DESERT, 
IN WESTERN TEXAS. 
An analysis of the conditions to be met in this vast region, based upon 
an actual survey, has recently been made by Professor Bray (Vegetation 
of the Sotol Country, Bulletin of the University of Texas, Scientific 
Series No. 6, 1905), and the general results are set forth in the following 
paragraphs, collated from his paper on the subject: 
Eastern Texas has the characteristic humid and warm-temperate flora 
of the Gulf region, with the long-leaf pine (Pinus palustris), the cane 
(Arundinaria), bald cypress (Taxodium distichum), and associated species, 
with a rainfall of over 50 inches annually. Passing westward from the 
Sabine River, by well-marked steps, a pronounced xerophytic aspect of 
the vegetation is encountered west of San Antonio, 300 miles from the 
starting-point, and the desert character of the flora becomes very marked 
in the sotol country, 200 miles farther west, and takes on increased aridity 
in the region of El Paso, in the Chihuahuan Desert, with a rainfall of 
about ro inches yearly. 
Orange, on the Sabine River, has an elevation of only 12 feet above 
the sea-level and an annual rainfall of about 50 inches. The region com- 
prises a flat coastal plain, with low sandy ridges, river bottoms, and 
bayous. The vegetation includes cane (Arundinaria) and reed swamps; 
humid subtropical bottom-land forests, with magnolias, bay, pecan, hol- 
lies, oaks, gums; dense cypress and tupelo swamp forest, thickets of pal- 
metto (Sabal glabra); heavy forests of long-leaf pine and of loblolly pine. 
Houston, 60 miles to the westward of Orange, rises but 40 feet above 
sea-level and shows a slightly smaller amount of rainfall, the annual pre- 
