16 LIGHT IN RELATION TO TREE GROWTH. 
with a crown density of 0.7, there were isolated groups of suppressed 
young pines, among which were no old trees. The young pines were 
10 years old and but little over a foot and a half in height. Ditches 
10 inches deep were cut around these groups, and in this way all the 
roots extending from neighboring old trees were cut through to the 
depth of the ditches. The relative amount of light received by 
these groups of undergrowth was not affected by the experiment, 
since not a single tree was cut down or trimmed. 
The ditches were made in the spring. In the first summer the 
needles that appeared on the little pmes within the isolated groups 
had doubled the length of the preceding summer, the terminal shoots 
became longer, and this thrifty growth continued up to the time the 
results of the experiments were described (1904), while the same 
undergrowth outside the areas surrounded by the ditches preserved 
the same suppressed character. The old trees, whose superficial 
roots were cut through, apparently did not suffer, and none of them 
were uprooted by the wind. On the areas inside the ditches a rich 
flora sprung up during the first summer. Entirely unexpected, there 
appeared bellflower (Campanula), wild strawberry (/ragaria), 
hawkweed (Hieracium), sorrel (Rumex), ironweed (Veronica), wil- 
low herb (£'pilobium), star thistle (Centeurea), geranium (Gera- 
nium), violet (Viola), five finger (Potentilla), and other herbaceous 
plants, and in addition there sprung up a number of seedlings of 
birch and mountain ash. Most interesting and significant of all, 
however, is the fact that none of these species appeared in the neigh- 
boring stand. The herbaceous vegetation which was present on the 
ground before the experiment, such as sweet vernal grass (Anthoxan- 
thum), hair grass (Azra), bentgrass (Agrostis), and woodrush (Lwa- 
ula), and which had led a very precarious existence, developed luxu- 
riantly, so that the areas surrounded by the ditches bore green, suc- 
culent vegetation, in striking contrast to the grayish-brown ground 
cover of the rest of the stand. 
In another pine stand, 100 years old, growing on poor soil, several 
natural openings on which there were no old trees or young growth 
of any kind were surrounded by ditches and sown with seeds of 
Scotch pine, spruce, beech, and red oak without any preparation 
of the ground. Similar sowings were made on similar natural open- 
ings not surrounded by ditches. On the area inside the ditches there 
are now remarkably well-developed seedlings of pine and oak, 
although with characteristics peculiar to shaded plants, and also 
seedlings of beech and spruce. At a distance of some 7 or 10 feet 
outside of the ditches, although a part of the seeds did come up, the 
seedlings of pine, beech, and spruce were poorly developed from the 
start and soon died; the seedlings of oak which still persist have 
scarcely reached 1/5 the height attained by those inside the ditches 
