OSMOTIC CONCENTRATION OF TISSUE FLUIDS 
269 
experiments under way at the Station for Experimental Evolution, it 
was quite natural to think of the Tropical Laboratory at Cinchona, 
established by the New York Botanical Garden and later maintained 
by the British Association for the Advancement of Science and the 
Jamaican local government, as the most promising locus for such 
work. This station presents the advantages of furnishing living 
quarters and laboratory space on the edge of a primaeval montane 
rain forest within twenty miles of a point where ice, essential for the 
preliminary freezing of tissues for the extraction of sap, can be ob- 
tained. This was quite successfully packed over the Port Royal 
Mountains, through the Yallahs river valley and up to Cinchona on 
mule back by negro helpers. 
To Professor Bower and the other members of the British Associa- 
tion committee in charge of the Tropical Laboratory at Cinchona 
and to Mr. Wm. Harris, F.L.S., superintendent of public gardens 
and plantations, we are indebted not only for the use of the laboratory 
but for other courtesies that added to the success and pleasure of 
our work while in Jamaica. 
Characteristics of the Region Investigated. — The higher portions of 
the Blue Mountains are characterized by a relatively low but uniform 
temperature, by a large and well-distributed rainfall, accompanied 
by much fog and cloudiness and high relative humidity. 
The rainfall upon the northern is far greater than that upon the 
southern slopes of the mountains. The averages given by Shreve 
(1914) for the upper mountains, in which all our collections were 
made, are: 
Cinchona 105.70 inches 
New Haven Gap 1 13-85 inches 
Blue Mountain Peak 130.48 inches 
Notwithstanding the heavy rainfall there are neither ponds nor 
constant streams above 4,500 feet, but in places there are depressions 
on the higher portions of the main ridge of the mountains which are 
developed as sphagnum bogs. Below 4,500 feet the water emerges to 
feed numerous swift mountain streams. Transient water courses are 
found much higher. 
While the rainfall is large it is not comparable with the maximum 
precipitations known in other tropical plant environments. Further- 
more the amount varies greatly from year to year, both in quantity 
