202 



PLANT LIFE 



compound organism is made up largely deter- 

 mine the broad lines of possible development. 

 If we alter the species, whether of alga or of 



Fig. 23s. Transverse section through the thallus or frond of 

 a lichen (Peltigera canina). A, algal cells. 



fungus, we have seen that we correspondingly 

 affect the " species " of lichen, ,as determined 

 and denned by its own peculiar form and 

 properties i. e. its process of development. 

 Qf course, the combinations which are 



