208 



ELEMENTS OF BOTANY. 



Beside the pasture plants above mentioned there grow 

 such others as the bulrushes and hardback 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. 



260. The Weapons of Plants} ■ — Multitudes of plants 

 which might otherwise have been subject to the attacks of 



Fig. 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. 1S7. 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. 430. 



