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 
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ye Wage Sz Dee SAMY SONGS eh SON 
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Sap yi ep mia a so ENTS UA 
Seat ry 
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= —> ee > 
SSS FS 
——== 
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SSS 
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SSE Ss SZ — 
— 
Fig. 238.—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 defined by its own peculiar form and 
properties—~. e. its process of development. 
Of course, the combinations which are 
