114 FLOWERLESS PLANTS 



tures in connection with the hchen alhance is 

 its bearing upon the whole question of para- 

 sitism. The subject is a vast one, which can 

 only be touched upon very briefly. There is 

 a good deal of reason for believing that in man}' 

 instances the outcome of parasitism is a much 

 more satisfactory state of affairs. In extreme 

 cases the parasite forces its attention upon its 

 host to such an extent that, more often than 

 not, the object of attack is killed altogether. In 

 the case of the lichen alliance the fungus is a 

 parasite, but, far from killing its hosts, it 

 makes life easier for them. It is surely the better 

 plan to keep on good terms with hosts who are 

 serving you well, and so continue to receive 

 favours, than to plunder to such an extent 

 that you rob them of even life itself. Instances 

 of this symbiosis, as it is called (hterally, a 

 living together), are nowadays continuallj' being 

 brought to light, and the reader is referred to 

 the chapter on Fungi in the present volume 

 for another very remarkable case. 



Of all plants, lichens are perhaps the most 

 dependent upon atmospheric moisture, so that 

 the business of securing a sufficiency to keep 

 the httle colony in an active state is not a 



