CHAP, in.] PROTECTIVE ARRANGEMENTS. 115 



can be turned to account, and consequently lead to the 

 destruction of the individuals they were designed to 

 protect. Our common arum (Arum maculatum) , popularly 

 known as " Lords and Ladies/' has an intensely acrid 

 substance present in the leaves, which effectually protects 

 it from the attacks of mammals and caterpillars, but not 

 from the attacks of parasitic fungi, which appear to be 



Fig. 33. " Lords and 

 Ladies " (Arum macu- 

 latum), a plant that 

 protects its leaves from 

 mammals and insects 

 by the presence of an 

 acrid substance. (Re- 

 duced. ) 



indifferent to all protective contrivances exhibited by 

 plants, nearly every plant supporting one or more of 

 these minute pests, the effects of which will be realized 

 by mentioning the potato disease, " rust " and " smut " 

 in the various cereals, and the hop disease, all due to 

 parasitic fungi. The leaves of many exotic evergreens 

 are often much injured by the presence of parasitic 

 lichens that spread over the surface. 



