MUTUALISM. 91 



ptmctatuQii (Fig. 129). As other exumples may be mentioned 

 quince leaves, which I infected with Gymnosporangmm davariac- 

 forme, and leaves of Cynanchinn Vincctoxicv.m infested witli 

 Cronartium asclepiadaiin. In all these cases, nutritive sub- 

 stances seem to be still transmitted to attacked parts after 

 death of the rest of the leaf. The attacked spots show also 

 an independent behaviour in that they do not turn yellow 

 before the fall of the leaf, l)ut continue to work at the 

 service of the parasite. One can even believe that these green 

 islands, so long as inorganic substance and water are supplied 

 to them, live with the fungus like lichens, especially those 

 lichens whose algae obtain water and inorganic material direct, 

 not tlirough the fungal-hyi^hae. 



