4 BOTANICAL GAZETTE [JULY 
which temperature plays quantitatively and qualitatively in the 
distribution of bog plant societies is in the main not known. So 
far as the writer is aware, no quantitative measurements between 
temperature as a probable causative or limiting factor and the 
resulting function and form in bog plants has been previously 
conducted, such as would afford any definite record of the actual 
physical conditions obtaining at different substratum levels in a 
bog vegetation. What has been said for temperature holds true 
also for evaporation. The influence of this and other factors is 
among the pressing problems of physiological ecology. From this 
point of view the data presented below have been collected in the 
field during the past three years. 
The physical factors which modify and more or less control 
the community of plants on Cranberry Island have been formu- 
lated for the most part quantitatively. Yet it must be frankly 
admitted that, at the present time, interpretation of the data thus 
far gained is still only in-part possible. Though the data have 
been gained laboriously through many months, and to the writer 
seem convincing, to attempt to correlate these accurately may be 
ill-advised. Only by the multiplication of such data will it be 
possible to express the results with quantitative exactness. The 
very necessity, however, of recording and accumulating an 
extended series of comparative observations is the justification 
of publishing now the data at hand. The conclusions here 
expressed, therefore, are still tentative, and true for the local 
investigation only. 
Frequently the writer’s students have assisted in this work, 
and acknowledgment is due to Messrs. L. W. SHERMAN, E. 
Wricat, E. Linn, L. Kine, and M. G. Dickey for efficient aid. 
The warmest thanks of the writer are expressed here also to 
Professor J. R. CHAMBERLAIN, who surveyed the island, to Pro- 
fessors N. W. Lorp, W. E. HENDERSON, and C. W. Foutk for 
cooperation in the chemical analyses, and to Miss F. DETMERS 
for identification of plants and the care with which the floristic — 
study has been generally furthered. The expense of the field 
work has been covered in large part by a special grant from the 
Emerson McMillin Research fund. 
