ECOLOGY OF LEAVES 



125 



146. Cutting Leaves. — Some grasses and sedges are 

 generally avoided by cattle because of the sharp cutting 



edges of their 

 leaves, which will 

 readily slit the 

 skin of one's hand 

 if they are drawn 

 rapidly through 

 the fingers. Un- 

 der the microscope 



the margins of 

 90. Euphorbia splendens. 



The spines are dead and dry 



^^;^.^g^^ stipules. 



\^ _^,<^%^ such leaves are seen to be 



■ — j' 'S^ regularly and thickly set with 



■^J \ sharp teeth like those of a saw 

 (Fig. 92, c, d). 



147. Offensive or Poisonous 

 Plants. — A disgusting smell is one of the 

 common safeguards which keep plants from 

 being eaten. The dog-fennel, the hound's- 

 tongue (Cynoglossum), the jNIartynia, and 

 the tomato-plant are common examples of 

 rank-smelling plants which are offensive 

 to most grazing animals and so are let 

 alone by them. Oftentimes, as in the case 

 of the jimson weed (Datura), the tobacco- 

 plant, and the poison hemlock (Conium), 

 the smell serves as a warning of the poi- 

 sonous nature of the plant. A bitter, nauseating, or biting 

 taste protects many plants from destruction by animals. 



Fig. 91. Thorn 



Stipules of 



Locust. 



