180 



AGRICULTURE ON THE PACIFIC SLOPE 



stems are very difficult to destroy. Only constant 

 cutting will check it. 



Perennial Grasses. The worst of these is the famous 

 Johnson grass. The salt grass is also troublesome in 

 alkali soils. 



POISONOUS PLANTS 



Poison oak, or poison ivy. While not poisonous to 

 animals, it is so to many people. The poisonous sub- 





FIG. 96. Poison oak or poison ivy. 'The leaves are in groups of three. 

 The berries are shown at the left. 



stance is an oil, of which any alkali will destroy the 

 poisonous action. Hence, if the skin is washed with 



