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TEXTBOOK OF BOTANY 



Fig. 223. Festoons of Spanish moss {Tillandsia usneoides) pendant on the 

 branches of a hve oak in Florida. Spanish moss is a member of the pineapple 

 family. Photo by G. W. Blaydes. 



from living plants. A grasshopper climbs upon a plant and eats its young 

 leaves, while a cow roams over the pasture and eats the live leaves of 

 grasses. 



A mistletoe which grows on a variety of trees in the southern half of 

 the United States is a good example of a partial parasite ( Fig. 224 ) . Its 

 sticky seeds adhere to the branches of trees; and when one of them 

 germinates, a root-like haustorium grows through the bark to the con- 

 ductive tissues of the host. The stems and leaves of this mistletoe con- 

 tain chlorophyll, and some sugar is synthesized in them. Water and 

 salts are of course obtained from the soil through the host. No one knows 

 at present what percentage of the food of the mistletoe is obtained from 

 the host, or whether it can develop under experimental conditions in 

 the absence of a host. The relation of such plants as the mistletoe to 

 their hosts is similar to that of a grafted scion to the stock. 



An analogous partial parasitism occurs when the root tips of green 

 plants penetrate the roots of other green plants and become haustoria. 



