208 ELEMENTS OF BOTANY. 
Beside the pasture plants above mentioned there grow 
such others as the bulrushes and hardhack of New England 
and the ironweed and vervains of the Middle 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 knotgrass and cinquefoil of our dooryards, are doubly 
safe, from their growing so close to the ground as to be hard 
to graze and from their woody and unpalatable nature. 
250. The Weapons of Plants..— Multitudes of plants 
which might otherwise have been subject to the attacks of 
Fic. 187.— Thorn Leaves of Barberry. 
grazing or browsing animals, have acquired what have with 
reason been called weapons for defense. Shrubs and trees 
not infrequently produce sharp-pointed branches, like those 
of the broom, Fig. 186, familiar in our own crab-apple, wild 
plum, and above all in the honey locust, whose formidable 
thorns often branch in a very complicated manner. 
Thorns which are really modified leaves are very perfectly 
exemplified in the barberry, Fig. 187. It is much commoner 
to find the leaf extending its midrib or its veins out into 
spiny points, as the thistle does, or bearing spines or prickles 
1 See Kerner and Oliver’s Natural History of Plants, vol. I, p. 480. 
