TIlALLOrilYTES: FUNGI 297 



pendently of the fungus. In fact, the enmeshed Algfe are 

 often recognized as identical with forms living indejX'nd- 

 ently, those thus used being various Blue-green, Protococ- 

 cus, and Conferva forms. 



On the other hand, tlie fungus symbiont has become 

 quite deiDcndent upon the alga, and its germinating spores 

 do not develop far unless the young mycelium can lay hold 

 of suitable Algae. At certain times cupi-like oi- disk-like 

 bodies appear on the surface of the lichen thallus, with 

 brown, or lilack, or more brightly-colored lining (Figs. 270, 

 271 ). Tliese bodies are the (ipothecia, and a section through 

 tJiem shows that the colored lining is largely made up of 

 delicate sacs containing sp(M-es (Figs. 273, 274). These sacs 

 are evidently asei, the apothecia correspond to ascocarps, 

 and the Lichen fungus proves to be an Ascomyceto. 



m 



Fi(;i.27."i. S(-^cti(in tliroii^h an apothecium of Anaptijclda. slunviriL' stalk of ttie cup 

 (m), maspes of algal cells ig), oiitt-r inaririn of cup (/■), overla]>|)inir cil^^c {(. /), layer 

 of asci (/;), and massing of liypli;e beneath asci (yl.— After Sachs. 



Certain Ascomycetes, therefore, have learned to use cer- 

 tain Algre in this peculiar way, tind a Lichen is the result. 

 Some Basidiomycetes have also learned the same habit, and 

 form Lichens. 



Various forms of Lichen bodies can be distinguished as 

 follows : (1) Crustaceuus />*(7/e«.y, in which the thallus resem- 



