OAliPOPEYTA. 



167 



tioally. These protophytes, -which 

 live in the midst of the moist tis- 

 sues of the lichens, were until re- 

 cently supposed to be parts of the 

 lichen itself, and were called go- 

 nidia, a term which it is still con- 

 venient to use. A few lichens are 

 parasitic in this way upon plants a 

 little higher than protophytes. 



351. The spores of lichens are 

 produced in sacs, which are either 

 in discs (similar to those of Cup- 

 fungi) or in cavities (similar to 

 thcce of the Black Fungi). In 

 many common species the spore- 

 bearing discs (called apotheoia) 

 are large and readily seen (Fig. 90, 

 A and B), while in others they are 

 small and not easily made out. In 

 other species the spore-sacs are im- 



Fia. 91. 



Fia 93. 



Fig. 91.— Gonidia of different Lichens, showing attachment of the parasitic 

 filaments: several are dividing. All highly magnified. 



Fig. 93.^A vertical section of a common Lichen (Physcia stellnris) through a 

 I'ruit-disc, showing spore-sacs at th^ intermingled with slender filaments (para- 

 physes), t\ gonidia at gr, g'; cm, the interlacing branching filaments, becoming 

 hai'dei' and denser at cc and h. Much ma^ifled 



