216 PHYLUM VII. CARPOMYCETEAE 



tion and ample opportunity for growing. There is thus 

 an association between these plants which is mutually 

 beneficial (symbiosis) ; the fungus lives parasitically upon 



the green algae, to which in return it furnishes 



shelter and moisture. 



344. Among the Disk Lichens one of the 

 simplest is the Thread Lichen (Epbebe) found 

 on wet rocks. In it the fungus filaments 



FIG. 97. grow over and around the cells of Scytonema 



Ephebe _,,. 1 



(parasitic on or Stigonema filaments. 



345. Some other Disk Lichens are parasitic 

 upon Nostoc colonies, as in the Jelly Lichens (Collema, 

 Leptogium), while for the greater part they are parasitic 

 on species of Protococcus, as is the case with the great 

 majority of common lichens Cladonia, Theloschistes, 

 Physcia, Parmelia, Ramalina, Usnea, etc. 



THE CUP-FUNGI (ORDER PEZIZALES) 



346. The common Cup-fungus of the woods is a typical 

 representative of this order. The familiar cup- or saucer- 

 shaped growth is in reality the spore-fruit ("apothecium"), 

 while the plant itself is out of sight. The plant consists 

 of whitish, septate filaments which grow on or in the 

 ground or in rotten wood, drawing their nourishment from 

 decaying vegetable matter. These plants are therefore 

 saprophytes. Some Cup-fungi, however, are known 

 to be parasites. 



347. But little is known as to the asexual reproduction 

 of the Cup-fungi, but in some species conidia have been 

 observed. 



348. The sexual organs of Pyronema("Peziza") are pro- 

 duced by the swelling up of the ends of certain of the fila- 

 ments of the plant into globular or ovoid cells, the oogones, 

 each having a projection (trichogyne) . From below each 



