THALLOPHYTES : FUNGI 
297 
pendently of the fungus. In fact, the enmeshed Algae are 
often recognized as identical with forms living independ- 
ently, those thus used being various Blue-green, Protococ- 
cus, and Conferva forms. 
On the other hand, the fungus symbiont has become 
quite dependent upon the alga, and its germinating spores 
do not develop far unless the young mycelium can lay hold 
of suitable Algae. At certain times cup-like or disk-like 
bodies appear on the surface of the lichen thallus, with 
brown, or black, or more brightly-colored lining (Figs. 270, 
271). These bodies are the apothecia, and a section through 
them shows that the colored lining is largely made up of 
delicate sacs containing spores (Figs. 273, 274). These sacs 
are evidently asci, the apothecia correspond to ascocarps, 
and the Lichen fungus proves to be an Ascomycete. 
FIG. 273. Section through an apothecium of Anaptychia, showing stalk of the cup 
(m), masses of algal cells (g), outer margin of cup (?), overlapping edge (t, t), layer 
of asci (/t), and massing of hyphse beneath asci (y). After SACHS. 
Certain Ascomycetes, therefore, have learned to use cer- 
tain Algae in this peculiar way, and 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) Crustaceous Lichens, in which the thallus resem- 
