Vegetal Evolution. 141 



vegetals but on animals, they rival the highest vegetal 

 carnivora. The habits of the two, however, are quite 

 dissimilar. 



One fungus (chytridicce) consists only of a sporangial 

 cell which attacks fresh water alg?e and infusoria. It 

 is maintained in position by, and draws its nourish- 

 ment through, a haustorium (or rootlet) which pene- 

 trates the host cell. (The victim of a parasite is 

 termed the host). 



Evipusa muscat is a fungus common on the ordinary 

 house-fly which ramifies its rootlets through the insect's 

 body. The salmon disease is caused by the sapro- 

 legnia ferax — a fungus both saprophytic and parasitic, 

 for it attacks the salmon alive or dead. Besides 

 fungi, other vegetals more exalted in the scale of life 

 are equally dependent upon other plants for subsist- 

 ence. Thus the dodder (cuscutd) first entwines its 

 victim, then penetrates it with its haustoria as far as 

 the vascular system, and thenceforth draws all its 

 nourishment from it, its own root dropping off and 

 connection with the soil entirely ceasing. 



The mistletoe adheres by its viscid fruit to various 

 trees (apple, lime, elm, maple, willow, thorn, popkr), 

 and on the seed germinating, its rootlets penetrate 

 the wood and absorb the juices ; the robbery often 

 causing the deformation of the limb to which it is 

 attached. 



The dependence of vegetal parasites upon hosts 

 results, as already said, from the absence of chlorophyll, 

 and consequently from an inadequate supply of assim- 



