ECOLOGY OF LEAVES 123 
So too with leaf-eating insects and snails, which consume 
great quantities of leaves. 
143. Plants of Uneatable Texture. — Whenever tender 
and juicy herbage is to be had, plants of hard and stringy 
texture are left untouched. In pastures there grow such 
perennials as the bracken fern and the hardhack of New 
England and the ironweed and vervains 
of the Central States, which are so harsh 
and woody that the hungriest browsing 
animal is rarely, if ever, seen to molest 
them. Still other plants, like the knot- 
grass and cinquefoil of our dooryards, 
Fic. 88. Spiny Leaves of Barberry. 
are doubly safe from their growing so close to the ground 
as to be hard to graze and from their woody and unpala- 
table nature. The date-palm (which can easily be raised 
from the seed in the schoolroom or the laboratory) is an 
excellent instance of the same uneatable quality found in 
a tropical or subtropical plant. 
144. Plants with Weapons for Defense.!— Multitudes of 
plants, which might otherwise have been subject to the 
1 See Kerner and Oliver’s Natural History of Plants, Vol. I, p. 480. 
