1915] CURRENT LITERATURE Ti 
far into Polynesia, fading out gradually instead of stopping abruptly. Simi- 
opposing the view of WALLACE. Starting from this sure foundation, HALLIER 
sets out on the perilous task of constructing land bridges between present-day 
islands and continents. He believes that Indonesia, Australia, and Polynesia 
were once connected, the islands now existing having been the mountain peaks 
of this former continent. In still older times Haturer believes that Austral- 
asia and Polynesia were connected by a wide land bridge with America, the 
northern boundary extending through the Sandwich Islands to Lower Cali- 
fornia and the southern boundary extending from the southern islands of New 
Zealand, south of the Society Islands, through Easter Island and Juan Fernan- 
dez to southern Chile. Hattrer’s views recall the submerged continent 
postulated by Darwin in connection with his theory of the origin of coral 
islands; nowadays, however, geologists seem to be getting more and more 
convinced of the relative permanency of oceans and continents, at least through- 
out the more recent ages. The possibilities of plant migration in our present 
world are so very large that botanists may well leave to the zoologists the 
construction of extensive land bridges and the arbitrary submergence and 
emergence of continents.—H. C. Cow Les. 
Evaporation and plant succession.—Among the recent contributions of 
quantitative data concerning the factors causing the succession of plant associa- 
tions is a study by WEAVER” of the evaporation conditions within certain 
grassland and forest associations of Washington and Idaho. The succession is 
from the prairie to a climax forest of cedar (Thuja plicata), and the record 
extends over 126 days beginning May 7, 1912. The average daily amounts of 
evaporation for the various associations taken in the order of their occurrence 
in the succession are, approximately, bunch grass 28 cc., prairie with southwest 
exposures 23 cc., prairie with northeast exposure 17 cc., yellow pine (Pinus 
ponderosa) 12 cc., fir-tamarack 9 cc., and cedar forest 8 cc. These atmospheric 
conditions are further compared, and using those of the mesophytic cedar forest 
as the standard of reference, it is found that “in the fir-tamarack associa- 
tion from May to September, atmospheric conditions in the lower stratum are 
120 per cent as severe, in the average prairie of the plains 250 per cent, and in 
the bunch grass association 345 per cent as unfavorable for plant life as regards 
the evaporating power of the air.”’ Moreover, the conditions in the mesophytic 
forest are found to be almost identical to those recorded by the reviewer* for 
the climax mesophytic forest of the eastern United States as determined in 
* WEAVER, J. E., Evaporation and plant succession in southeastern Washington 
and adjacent Idaho. Plant World 17:273-204- 1914. 
* FULLER, G. D., Evaporation and plant succession. Bor. Gaz. $2: 193-208. 
IQIr. 
