ECOLOGY OF LEAVES 125 
146. Cutting Leaves.—Some grasses and sedges are 
generally avoided by cattle because of the sharp cutting 
edges of their 
8, leaves, which will 
rg readily slit the 
skin of one’s hand 
if they are drawn 
rapidly through 
the fingers. Un- 
der the microscope 
the margins of 
Fic. 90. Huphorbia splendens. 
eee if The spines are dead and dry 
” ipules. 
SS, : stip 
Ne. such leaves are seen to be 
i$] regularly and thickly set with 
= MW sharp teeth like those of a saw 
LP (Fig. 92, ¢ 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 Martynia, 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 A 
of the jimson weed (Datura), the tobacco- Fic. 91. Thorn 
plant, and the poison hemlock (Conium), pee 
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. 
