126 THE EVOLUTIONIST AT LARGE. 



considerable haziness as to what a true 

 parasite is. The mistletoe is a plant which 

 has taken, it is true, to growing upon other 

 trees. Its very viscid berries are useful for 

 attaching the seeds to the trunk of the oak 

 or the apple ; and there it roots itself into 

 the body of its host. But it soon produces 

 real green leaves of its own, which contain 

 the ordinary chlorophyll found in other 

 leaves, and help it to manufacture starch, 

 under the influence of sunlight, on its own 

 account. It is not, therefore, a complete 

 drag upon the tree which it infests ; for 

 though it takes sap and mineral food from 

 the host, it supplies itself with carbon, which 

 is after all the important thing for plant-life. 

 Dodder, however, is a parasite pure and 

 simple. Its seeds fall originally upon the 

 ground, and there root themselves at first 

 like those of any other plant. But, as it 

 grows, its long twining stem begins to curl 

 for support round some other and stouter 

 stalk. If it stopped there, and then produced 



