26 BOTANICAL GAZETTE [JANUARY 
(one a clump of three stump sprouts) and a 20-year old birch in the 
lower right-hand corner. The young growth is not evenly dis- 
tributed, but shows a tendency toward grouping, which tendency 
will be seen in each of the succeeding quadrats. The larger number 
of trees of each group are approximately even-aged. For example, 
the rather scattered group a that surrounds the 5 balsam stumps 
contains 13 balsams, 10 of which are 23-28 years old. Of the 18 
trees in group 0, 14 are between the ages of 30 and 50, not so uniform 
as the last, but decidedly of a single generation. Of the 13 trees 
in group ¢, all but the mountain ash and the large spruce are under 
30 years. 
Group a illustrates in a striking manner the way in which these 
even-aged clusters come into existence. Within its limits were 5 
large rotten balsam stumps from which the trees had been broken a 
meter or more above the ground. The group evidently constitutes 
a windfall, probably caused by a single storm, one tree in its fall 
carrying others with it. Such windfalls of various ages are exceed- 
ingly numerous throughout the forest, the balsams, on account 
of their brittleness and susceptibility to fungus attack, being the 
ones most frequently destroyed. This particular windfall is of 
special interest because it was possible to determine the time at 
which it occurred. One of the large balsams in falling pinned to 
the ground a young tree of the same species, which, in spite of 
unnatural position and dense shade caused by the branches of 
the fallen one, has continued to live up tothe present. The younget 
tree was 49 years old, and the first 12 rings were exceptionally wide, 
showing that up to the age of 12 years it was an unusually vigorous 
sapling. At this point a sudden change becomes evident, for the 
remaining rings are so close that in counting them a magnifying 
glass was an absolute necessity. This change could have been 
brought about only by some sudden and violent cause, and this 
cause is evidently to be found in the fall of the older tree. The 
windfall is therefore to be dated about 37 years ago. Returning 
to the trees composing group a, we find that they are all balsams; 
one is 85 years old, another 38, a third 14, and 10 range from 23 
to 28; 11 then are subsequent to the windfall, and 10 began life 
