172 
FRANK C. GATES 
The results and their interpretation follow: Taking up the hard- 
wood series first, the following results were obtained. In the area cut 
over during the winter of 1 914-15, where sufficient time had not yet 
elapsed for weeds to invade and change the evaporating conditions of 
the ground layer, the rate of evaporation was 590 and 561 cc. for 40 
days in the middle of the summer of 1915. This rate was 3.37 times 
as great as that from the floor of the normally dense hardwood forest 
in this region. In the area cut during the winter of 1913-14, where 
weeds and brambles had entered in quantity, the evaporation rates 
were 416 and 425 cc. from two stations. A relative slowing up of the 
rate of evaporation even during the season was plainly evident in 
atmometer No. 4, as the development of weeds during the course of 
the season came to protect the instrument and the Acer seedling to a 
greater and greater degree. In fact this protection from weeds was 
sufficient to cause a lower rate of evaporation than was obtained from 
atmometer No. 3 run in an open weedless spot in an area where hard- 
woods had made considerable progress in revegetating a former cut. 
There, the rate was 453 cc. during the same length of time. At the 
edge of the woods, where atmometer No. 6 was stationed in a luxuriant 
growth of Acer saccharum seedlings, a rate of 378 cc. was obtained for 
the period of experimentation. Ninety meters in from the margin, 
the rate had decreased to 240 cc. Within the woods the rate was 175 
cc. in a spot of average density, 147 cc. in a very dense situation, and 
187 cc. in a small opening in the dense forest. These results show a 
wide range of conditions from bare ground without shade — the severest 
conditions maple seedlings could be called upon to withstand — to the 
mature forest with its dense shade. Seedlings in the open received 
sunlight. Under more advanced conditions in the vicinity it was seen 
that such seedlings were developing into trees, while the vast majority 
of the multitudes of seedlings in the dense forest did not persist for 
more than a year or two, unless they were in openings. 
This is a clear case in favor of the contention that the seedlings of 
the dominant species of certain associations become established ir- 
respective of the evaporation conditions — in fact, with the addi- 
tional advantages accruing from an increased amount of sunlight, 
seedlings of mesophytic species thrive better under more xerophytic 
conditions than that which the mature forest furnishes. 
In the presence of sunlight. Thuja seedlings readily develop in either 
sandy or boggy soil, having a sufficient supply of water, under the 
