THE PLANT WORLD. 
190 
living, but very largely this is with some limitations and reserva¬ 
tions. I remember the exclamation of a student in my laboratory, 
to whom I showed some unusually active low form of plant— 
“ Why it's alive! ” Yet I had talked and lectured to that student 
in regard to the life of plants, and all that I had said had not 
penetrated sufficiently to make him realize that life in the plant 
is like life in the animal. It was only when this life manifested 
itself in visible motion that its full meaning was understood. 
Plants are alive, and their life is the same as that of animals. 
Not only is this true, but the life of a plant resides in the same 
substance in both kinds of living things. If we examine the 
animal substance under a compound microscope we find that it 
consists of very minute bodies which are composed of proto¬ 
plasm—a soft and somewhat slimy substance. And so if we 
make a similar examination of the plant substance we find simi¬ 
lar minute bodies, also composed of protoplasm. Now it is this 
essential identity of structure, and the actual identity of life, that 
I must insist upon here. The teacher who is trying to get an 
adequate notion of the pathology of apple trees, for example, 
must realize that they are actually alive as are horses and cattle, 
and that in their minute structure they are essentially alike. 
Some Differences Between Plants and Animals. 
Now while apple-trees and horses are essentially alike as liv¬ 
ing things, they differ in certain particulars. For example the 
tree has roots and leaves, while the horse has a mouth, a stomach, 
and blood-vessels. The digested food of a horse is carried 
rapidly to all parts of its body through a system of tubes—the 
arteries and veins—but in the apple-tree the food of all kinds 
merely soaks through the substance and has no tubes through 
which it runs. But in this the apple tree is like some lower 
animals, in which there is no system of arteries and veins, and as 
a consequence the digested food passes from part to part by a 
soaking process similar to that in the apple-tree. All animals 
having such a slow circulation are sluggish, some of them being 
almost as slow and sluggish as are the trees. It is noticed that 
just as animals are more active, their circulatory system is more 
perfect. 
