42 GENERAL BIOLOGY. 



(c) A thick, pure white layer : medullary 



layer. 



(d) A dark-colored, external layer : lower 



cortical layer. 



Sketch. 



2. Place a small piece of the thallus in water on a 

 slide and tear it apart ivith needles as com- 

 pletely as possible. Cover and examine ivith 

 D 2. Observe : 



(a) The hyphse. Disregard the broken frag- 



ments and search for specimens in their 

 natural condition. 



(b) The gonidia. Observe : . 



Cell wall. 



Chlorophyll. 



Nucleus (not always visible). 

 Sketch a few hyphse and gonidia to show their 

 form, their relative size, and the manner in 

 which they are connected. 



