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 
a « Fie. 90. Euphorbia splendens. 
ae 7 i The spines are dead and dry 
eet i stipules. 
My’ FARK. such leaves are seen to be 
we 
TPS Yeoularly and thickly set with 
at sharp teeth like those of a saw 
{~ (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 ‘I 
rank-smelling plants which are offensive 
‘ Vs 
to most grazing animals and so are let 1 \ 
alone by them. Oftentimes, as in the case a 
of the jimson weed (Datura), the tobaeco- Fic. 91. Thorn 
Stipules of 
ant, ¢ mlock (Contum 
plant, and the poison hemlock ((% iF a omeee 
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. 
