Southeastern Washington and Adjacent Idaho. 23 
with a consocies of yellow pine, above which, and still on the 
north slope, the Festuca consociation continues. The atmometers 
in the Agropyron community were installed about half way up 
the bank of the canyon. Those in the pines were placed in a 
9 8 
———+—_ T_| 
Soon 
aS eee 
| 2S NS a ae 
SENSE 
AS eee eee 
TB eee 
Fic. 3. Evaporation rates in the Agropyron, Festuca, and Pinus communi- 
ties at Colfax, Washington. 
A 
similar position on the opposite bank, and about 60 feet beyond 
these a station was established in the Festuca consociation. 
Graphs of the data from these instruments have been plotted in 
Fig. 3. 
These graphs show a striking decrease in the evaporating power 
of the air as the progressive stages of vegetational development 
are approached. During 1912 preliminary measurements indi- 
cated just such conditions in these communities. Stations main- 
tained at Pullman during 1913, showed similar differences in 
evaporation between the Agropyron and Festuca consociations, 
while during 1914 further data at Colfax confirmed in general 
the above results. 
23 
