174 
FRANK C. GATES 
foliage of the trees around the opening greatly checked the circulation. 
Likewise atmometer No. 34 by a small Thuja seedling in the marginal 
foss at the foot of a high ridge, where air drainage was poor, gave 391 
cc, a lower result than the 435 cc. from No. 33, which was further in 
the bog, but free from the influence of ground vegetation owing to 
the dense canopy of Thuja saplings. 
Atmometer No. 36, run in a small relic bog in the aspens north of 
Reese's bog gave 335 cc. and atmometers No. 37 and No. 38, run in a 
slashed bog to the east of Douglas Lake, gave 344 and 307 cc. re- 
spectively. In each case Thuja seedlings were developing at a rapid 
rate. Based upon one week's record, the evaporation near a Thuja 
seedling on the beach for the season of 1916 would have been 562 cc. 
and 487 cc. at the edge of the beach thicket. 
In the pine series, investigated during 191 5, the evaporation varied 
from 347 cc. in an open spot in an aspen grove, through 310 and 321 
cc. on an exposed hillside, 197, 198, 196, and 187 cc. in the ordinary 
aspen association to 178 cc. at the foot of a slope in the densest part 
of the aspens. In each case the results express the conditions with- 
stood by one to three-year-old pine seedlings of which there were large 
numbers throughout the aspens. Pine seedlings easily withstand as 
wide a range of conditions as the region presents. In no case therefore 
could it be said that evaporation conditions were the determining 
factor in their ecesis. The presence of all ages and sizes of pine trees 
is excellent evidence of how well the pine is developing and in con- 
sequence the succession is progressing. Aspen seedlings are abundant 
in the open sandy ground. As they develop, the increasing shade and 
the checking of the wind are instrumental in causing a decrease of 
evaporation from the chamaephytic layer, for example, atmometers 
No. 18 and No. 24, with rates of 315 and 196 cc. respectively. 
The two atmometers run during 191 5 in connection with the area 
south of Bryant's, the one in pine land and the other in hardwood land 
— each of which was very openly vegetated — gave the following 
results : The evaporation from the immediate vicinity of a pine seedling 
in pine land was 513 cc. Atmometer No. 13, run in hardwood land 
devastated by fire, one and one half months previous, gave a rate of 
473 cc. for the same period. The fact that the evaporation rate was 
473 cc. in the hardwood land, where maple seedlings were present, 
and 513 cc. in the pine land, where pine seedlings were present, whereas 
maple seedlings developed successfully under the highest rate (590 cc.) 
