PARASITISM 337 



Other striking examples are the mistletoes. These 

 plants, of which hundreds of species are known, produce 

 berries full of a very viscid juice which serves to glue the 

 seeds to the branches of the trees upon which they 

 germinate, the little rootlets striking upward and pene- 

 trating into the tissues of the host from which the para- 

 site derives its nourishment. The stem continually 

 forks dichotomously, each branch terminating in a 

 pair of fleshy leaves. The flowers are small and appear 

 at the ends of the branches and in the small divisions. 

 As the plant is evergreen it forms a striking object in 

 winter when it appears as a thick tangle of tiny green 



FIG. 114. Bastard toad-flax (Thesium alpinum). 1. Root with suckers; 

 almost natural size; 2, piece of a root, with sucker in section. X about 35 

 (Kerner and Oliver.) 



leaves and stems upon the otherwise bare branches 

 of many common trees. 



A peculiar form of vegetable parasite is the "bastard 

 toadflax," a rather pretty flowering plant. What can be 

 seen above ground is an independent plant with stem, 

 leaves, and flowers of its own, but below ground its roots 

 attach themselves to the neighboring roots of other plants 

 which it robs and thus dwarfs. 



22 



