BOT.-VOL. I.] FEIRCE— NATURE OF LICHENS. 237 



III. Though algae may not always grow independently 

 where they are found associated with fungi, forming lichens, 

 it is neither logical nor sensible to conclude that their unus- 

 ual position is beneficial to them. 



IV. Though the percentage of water retained by the 

 more or less gelatinous constituents of the lichen thallus is 

 hio-her than that which the gonidia could retain as free 

 organisms, the occurrence of healthy algae on the spots 

 subsequently occupied by lichens demonstrates that free 

 algte can thrive, at least for a time, wherever lichens can. 



V. Though it may be claimed that the individual gonidial 

 cells live longer in the Hchen than the free individual cells 

 of the same species of alga, there is no proof of this, and 

 if there were, it is well known that in their resting forms 

 free alg£e withstand extremes of heat, dryness, etc., as suc- 

 cessfully as do hchens and lichen gonidia. 



VI. There is no proof that algal cells serving as lichen 

 gonidia are any better off as to food, protection or situation 

 than the average free algal cells of the same species; 

 whereas it is evident that the fungus portion of every lichen 

 is absolutely dependent upon the gonidia for all of its non- 

 nitrogenous food. 



VII. As to Reinke's claim that the Hchens should be 

 regarded as plants as truly autonomous as trees and shrubs 

 because they have their own peculiar structure, growth, 

 habit, color, etc., as well as because there can be no lichen 

 without both components, an analogy may assist us to 

 clearer views. Bacteria grown in bouillon cannot form the 

 definite colonies of peculiar and characteristic structure, 

 growth, habit, color, etc., which the same species will form 

 on nutrient agar-agar or gelatine. To the formation of the 

 colony, with its characteristic peculiarities, the living bac- 

 teria and the lifeless but nutritious solid substratum are 

 both absolutely necessary. The bacteria may grow quite 



