LICHEN. 



I. External Characters. 



Examine ivith the naked eye the thallus of a green 

 foliaceous lichen e.g., Parmelia that has been 

 moistened tuith loater for several hours. Observe : 



1. Form. 



2. Color. 

 Sketch afeiv lobes. 



With a scalpel carefully separate part of a thallus 

 from the substratum. Observe : 



3. The difference in color between the two sides. 

 Place the specimen uncovered on a slide, the lower 



surface uppermost, and examine with AA 2 by 

 reflected light. Observe: 



4. Ehizoids. (Many will have been broken off 



and only their bases will show.) 



II. Structure. 

 1. Sections. 



With a razor make sections through the thick part 

 of a thallus ; or, the specimen may be rolled up 

 closely and, cross -sections of the roll may be made. 

 Mount (in ivater) so as to shoiv the cut surface. 

 Examine with A A 2 in strong reflected light 

 Observe : 



(a) A thin white superficial layer : the upper 



cortical layer. 



(b) A green layer : gonidial layer. 



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