72 



MORPHOLOGY 



bb. Formation of crustaceous tissues. Some crustaceous lichens have 

 a persistently scanty furfuraceous crust, the vegetative development never 

 advancing much beyond the first rather loose association of gonidia and 



Fig. 38 B. Young thallus of Rhizocarpon confervoides DC, with various 

 centres of gonidial growth on the hypolhallus x 30. 



Fig- 39- Lecanora parella Ach. Determinate thallus with white bordering 

 hypothallus, reduced (M.P., Photo.). 



