THE PATH OF EVOLUTION 



tion with the algae as a lichen. A few of the same 

 algae are known to exist with independent life as 

 Algce. Their union with the fungi gives rise to 

 numerous species of lichens. The Gonidia, or cel- 

 lules, con tain ing the globules of chlorophyll, are almost 

 identical with those of the Algae. Thus those of 

 Physica are like those of Protococcus; those of Col- 

 lema like those of Nostoc; those of Omphalaria like 

 those of Chroococcus, etc., etc. 



The experiment has been made of mechanically 

 separating the structures of the plants and cultivating 

 them apart. The alga, a Protococcus Viridis, 

 grew and multiplied readily. The fungus part 

 lived for a time, did not increase, and soon died. 

 The synthesis of a Lichen has been made by Gaston 

 Bonnier (Revue Ency., 1893). He caught the spores 

 of the fungus on a microscopic slide, and, after the 

 necessary precautions to avoid the entrance of foreign 

 germs, introduced a portion of the above-named algae. 

 The process, with the admission of pure air, was 

 watched under the microscope, and showed the de- 

 velopment in all its stages of a perfect and normal 

 Lichen. In this union of two lives the fungus fur- 

 nishes the hyphae that attach the plant to the rock ; 

 it also furnishes a shelter and support to the alga 

 and its spores through the extremes of heat and cold, 

 of drought and of excessive moisture; its own com- 



236 



