PLANTS DEFEND THEMSELVES 45 
the plants hardened their blades with silica. The 
common horsetail, a plant of this species, makes 
deadly sick those unwise cattle and sheep which 
attempt to eat it. 
There are many juices and poisonous secretions 
used by plants in defending themselves against 
animal life. One of the most common of these is 
tannin. It is found in the bark of many trees: 
in the beech, the walnut, the pecan, and the hickory, 
in the tropical acacia, in several of the oaks, be- 
neath the shells of nuts, and encasing the repro- 
ductive germ in most fruits. 
Here once more is evidence of the reasoning 
power of plants. Their one great aim is repro- 
duction—the perpetuation of their kind. To this 
end all thought and action in plant life is directed. 
It is for this reason that the winged insect, a pollen- 
carrier, is given entrée to the soul of the plant, while 
the crawler, not a pollen-bearer, is resisted with 
every power. To the plant mind or instinct, the 
preservation of the fruit is nothing—it is merely 
a soft covering for the germ inside; but the preser- 
vation of the germ, the reproductive possibility, is 
everything. Hence the fruit is an edible, inviting 
thing; but the “stone” or “pit” is a hard, indigesti- 
ble piece of “waste,” which is thrown aside. Thus 
it is provided an opportunity to germinate in new 
