a teacher's knowledge of plant pathology. 
193 
since they expose or destroy the cambium, and so stop the stem 
growth, often resulting in the early death of the tree. 
The third class of wounds includes those made by the owner 
himself when he prunes his trees. In many cases he is wise 
enough so to handle his trees that he does not have to remove 
large branches, thus avoiding the necessity of making large 
wounds. But in too many cases the tree is allowed to grow as 
it will for a number of years, and then when too many branches 
have started the top is severely pruned, leaving many open 
wounds through which fungi gain entrance, and in which decay 
sooner or later sets in. If these wounds in the top are accom¬ 
panied with wounds on the roots, due to careless transplanting, 
the tree is in a sad plight indeed. The wonder is that with 
so many gaping wounds the tree ever recovers. And there can 
be no question that these partially healed wounds are the cause 
of the early death of many a tree. Such trees are like the soldiers 
who have many wounds, from which they seem to recover for a 
time, only to find after a while that the old wounds which were 
only partially healed, finally drag them down to death. A 
wounded tree is like a wounded man; it may recover, but there is 
always danger that the wound is not fully healed, and may some 
day prove fatal. 
5. Loss of Necessary Parts .—All things considered the leaves 
are the most necessary organs of plants, and yet the leaves are 
frequently destroyed so that the plant is naked. Now, the leaves 
are not the clothing of the plant, as is supposed by some people, 
but they are much more like the stomach, in which the food is 
prepared so that it can be used by the plant. A plant without 
leaves is in practically the condition of an animal which has no 
stomach. Of course this is a very crude comparison, but it is 
true to this extent that both leaf and stomach are necessary 
organs in the preparation and digestion of food, on the one hand 
for the plant, and on the other for the animal. When insects eat 
the leaves of a plant they destroy to that extent its power to use 
the available plant food, especially that derived from the air. 
And this is the real nature of the injury to a tree when its leaves 
are lost whether by insects, frost, hail or any other means. The 
