162 A TEXT-BOOK OF BOTANY 
It has been found that the lichen-alga can live quite 
independently of the lichen-fungus. In fact, the enmeshed 
Alge are often recognized as identical with forms living 
independently, the forms usually being certain blue-green 
Fie. 158.—Much enlarged section of portion of lining layer, showing the asci 
(1, 2, 3, 4) with their contained spores.— After Sacus. 
Alge and some of the simpler green Alge. On the other 
hand, it has been found that the lichen-fungus is com- 
pletely dependent upon the Alge; for the germinating 
spores of the fungus do not develop far unless the young 
