March 9, 1894. 
the velocity of these currents at 5,000 ft. is double that 
at the earth, and any storm or high area would be very 
quickly disintegrated by such action. 
AUTUMN COLORING OF LEAVES. 
BY G. W. M’CLUER, CHAMPAIGN, ILL. 
THE subject of this paper was suggested to me more 
than a year ago by some highly colored leaves of the 
common red currant that I noticed while rambling in the 
woods near Urbana. 
I shall not take up my notes in the order in which they 
were made, or of their importance, but shall begin with 
the smallest. 
In the leaves of several species of trees where a principal 
vein has been broken, the part toward the tip of the leaf 
has colored earlier and more highly than the rest. Not 
unfrequently, in lobed leaves, the lobe with the broken 
rib has been the only part of the leaf that showed any 
coloring. Leaves torn from the margin to the midrib 
were not changed as a result of the injury. 
The species in which parts of leaves have been seen to 
color as a result of this injury are soft and hard maple, 
tulip, white, red and scarlet oak and cottonwood, and 
blackberry. Probably all plants that color at all would 
show the same thing. 
Carrying the observation a little further, branches of 
many kinds of trees and shrubs that have been girdled or 
otherwise injured, have been found to color earlier and 
usually, though not always, much more highly above the 
injured or girdled part than below, or than other branches 
on the same tree that were not injured. As noticed 
before, the thing that first called my attention to this 
subject was finding a clump of the common red currant 
with the leaves on the tips of several twigs colored dark 
crimson. An examination showed that all the twigs with 
colored leaves had been girdled by some insect while none 
of those still green were. Girdled grape branches fre- 
quently have very highly colored leaves, but I have never 
seen them colored on branches that were not injured. 
Girdled or injured branches with highly colored leaves 
have been noticed on all our native maples, on cotton- 
wood, elm, wild black cherry, oak, pear and plum. 
A large branch ona hard maple on one of our streets 
used to attract my attention, and I sometimes wondered 
if its habit of early coloring could not be perpetuated by 
budding from it. It was finally broken off and was found 
to be eaten by borers and partly decayed. Branches on 
some of the hard maples round which wires have been 
tightly drawn have colored earlier than the rest of the 
trees. Ina few cases where forked branches have split, 
the one nearest off has been found to be colored more 
than the other. 
The next step would be to find the whole tree 
highly colored than those around it on account of 
injury to the trunk. Believing that a variety of trees 
might be produced and propagated that would color 
regularly every fall, I have watched for such as might 
offer a good chance to try the experiment. In the arti- 
ficial forest belonging to the University is a plat of hard 
maple that has attracted my attention several times, but 
in looking at trees that were especially brilliant, it was 
found that all of them had some noticeable defect in the 
trunk; usually a place where the bark had been destroyed 
on one side of the tree and the wood left exposed so that 
it died. Ina group of hard maples like these there will 
frequently be found in the fall all gradations of color 
from plain green to bright yellow or red, at the same 
time. There is an individuality in time, depth, and 
shade of color that is entirely independent of the condi- 
tion of the tree itself. 
more 
some 
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N33 
Of four young soft maple trees near my house that 
were planted at about the same time, one has been allowed 
to get full of borers, and the trunk is so badly eaten that 
the tree will probably die before a great while, but last 
fall it was more highly colored than I had ever seen a 
soft maple before, and the leaves were all off of it before 
the others had fairly begun to turn. The brightest 
colored red oak yet seen had a barbed wire drawn tightly 
around it at about three feet from the ground, and the 
brightest Virginia creeper had had the bark knocked off 
in some way. 
It is now only one more step to the roots of the trees. 
We have on the University farm a plat of two year old 
white oaks that have been grown for planting in the arti- 
ficial forest. As a preparation for their removal, the top 
roots were cut last fall. The work was begun while the 
leaves were still green; when it was about half done, it 
was stopped and not completed until two weeks later. 
Within a week after the roots of the first had been cut, 
there was a very marked change in the foliage. The root 
pruned trees were all highly colored, while of those not 
pruned there was only occasionally one that had begun to 
color. 
It is a matter of common observation that trees on 
hilly land color more deeply than those on level land, but 
it is not so frequently reported that they also color earlier, 
though the latter is just as much a fact as the former. 
Trees on thin land color earlier than the same species on 
rich land. 
It is a common practice among nursery men to stop 
cultivation before the end of summer and allow the weeds 
and grass to grow, so that the trees will ripen up their 
wood earlier and more perfectly. Cultivated land holds 
moisture longer than uncultivated, and when the unculti- 
vated land has a coat of weeds and grass, the loss of 
moisture is still more rapid. 
It is a very common thing to see a clump of wheat or 
oats standing out at the edge of a field where it has things 
more to itself, that is much greener than the general 
field; or to see thick and thin spots in a field, and the 
thick always ripe earlier than the thin. Corn grown very 
thick ripens earlier than corn grown thin. A plat of corn 
on the Experiment Station grounds, that had no cultiva- 
tion this past year, the weeds being allowed to grow at 
will, ripened earlier than cultivated plats of the same 
variety on each side of it. This shows that the time of 
ripening depends on other circumstances than the indi- 
vidual character of the plant. 
It is not uncommon for our apple trees to shed many 
of their leaves during a season of severe drouth. If this 
is followed by heavy rains and warm weather, blossoms 
and new leaves are very apt to make their appearance. 
The age of a tree makes a difference in the length of 
time it uses to complete its season’s growth. Young 
trees, under like conditions, grow longer than older ones, 
and this is not a matter of shade either, for it is seen 
more decidedly in nursery stock, as compared with older 
orchard trees, than in trees in the forest. Sprouts from 
the stump of a tree that has been cut down grow later 
than trees of the same species near then. Water-sprouts 
in apple and other trees grow later than the normal 
branches; in fact there is but little difference in this 
respect between the water-sprout and the nursery grown 
apple tree. Both may be seen until the early winter 
with tufts of unripened leaves still adhering to their 
tips. 
This thought leads naturally to the subject of determi- 
nate and indeterminate growth of plants. 
Some species, as the oaks and ashes, will start out a 
shoot in the spring that reaches its full length in a short 
time, and the leaves expand and the wood hardens after- 
