ASCOMYCETES 



429 



are sometimes borne, as minute, non-motile bodies (spermatid), which 

 are produced in flask-shaped spermogonia, contained in the marginal 

 teeth of the thallus. Female organs have been seen in some of the 

 Lichens (Collema, etc.) to have the form of a coiled oogonium, with 

 a receptive trichogyne that projects to receive the non-motile sper- 

 matium, as in the Red Seaweeds. But it seems probable that in many 

 of the Lichens, as in many advanced Fungi, the sexual organs even 

 if morphologically present are not functional. 



A B 



Fig. 327. 

 Cladonia furcata. A = vertical section of the thallus showing the inverted gonidial 

 layer below the cortical sheath ( x 330). B =part of the same highly magnified, to 

 show the mode of attachment of the hyphae to the gonidia ( x 950). (After Bornet.) 



The establishment of a new Lichen from the germination of the 

 ascospore depends upon the presence of the algal partner. This 

 is not left to chance, but is provided for, in some cases at least, by 

 11 hymenial gonidia " : these are small algal cells which develop in 

 close relation to the asci. When the fungal spores are ejected some 

 of these adhere to their sticky walls, and thus the two partners 

 germinate together from the first. 



The close similarity in structure, nutritional behaviour, and pro- 

 pagative method with the Ascomycetes makes it probable that the 

 Asco-Lichens have arisen from Ascomycetous Fungi which have 

 adopted a symbiotic relation with Algae, and become dependent 



