286 BOTANICAL GAZETTE [OCTOBER 
of 1915 in a study of the osmotic concentration of the tissue fluids 
of the plants of the montane region. The results of this study will 
be published later. Fortunately, while in Jamaica we were 
also able to visit the remarkable coastal deserts of the southern 
shore. It seemed to us highly desirable to secure as large a series 
of determinations as possible upon the species constituting their 
flora for comparison with the observations already made in the 
Arizona deserts in the neighborhood of the Desert Laboratory. 
Our purpose in this paper, therefore, is to present a considerable 
series of novel physiological data on the plants of the desert area of 
the southern coast of Jamaica; to compare the flora in this regard 
with that of the southern Arizona deserts and of some other locali- 
ties; and to hazard some — concerning biological factors — 
immediately underlying certain of the differences observed in 
various species of the coastal region. 
_ CHARACTERISTICS OF DESERTS INVESTIGATED.—Lying as it does — 
in the center of the Carribean Sea, the island of Jamaica intercepts 
the trade winds in a way to cause a pronounced differentiation in 
its climatic conditions. This is especially true on the narrow 2 S 
eastern end, where the Blue Mountains, attaining a height of nearly = 
7500 feet, separate two narrow coast plains. At Port Antonio, at 
_ Sea level on the northern coast of the island, the mean annual 
ae -.con, at sea level oe 
= ‘ on the southern coast of the island, precipitation is on the average - : | 
ae less. than 38 inches per year. Temperature and insolation char 
acteristic of sea level at 18° N. latitude coupled with local peculiari- 
ties of the substratum have here resulted in & conspicuously ne 
rainfall averages more than 130 inches. At 
: _—_-xerophytic type of vegetation. 
sy the island from the mouth of the Cane River, just east of | oe 
for a distance of about 7o miles to the Pedro Bluffs. Its greatest oe 
_ As limited by SHREVES, the desert deers the southern oo of : Z 
SF ac is = in the Healthshire Hills, in the vi icir mad of ee 
