*^' III — ~ 



22 -— — ' 



3. Formation of the Lichen. 



Before the dissemination of the spores some of the 

 Gonidia crawl out of the parent plant and settle 

 themselves at some Httle distance off. They produce 

 the jelly and the large colorless cells, and so are ready 

 to become the hosts of the fungus. 



The spoies falling in their neighbourhood germin- 

 ate by putting out as a rule two filaments (hyphse) from 

 the endospore. They come in contact with the jelly of 

 the gonidia and grow and ramily in all directions, 

 until the little group of gonidial cells is entirely 

 invested by their threads (hyphae). A new lichen is 

 thus formed ; the young hyphse take up the necessary 

 food from the substratum, and convey it to the 

 gonidia, which assimilate it ; the gonidia use part 

 of it for the growth and multiplication of their own 

 cells, and give up the rest to the hyphse. The 

 thallus begins at once to produce the apothecia, 

 which in their turn produce the spores ; some of the 

 gonidia wriggle out and away to form a new host 

 for the germinating spores. 



Facts in support of the Algo-Lichen theory 



above discussed. 



1. If the green element be isolated from the 

 fungus and cultivated, it gives a life history 

 identical with some known alga. The alga of 

 Collema is Nostoc. 



