THE PLANT GKOUPS 101 



LICHENS 



Select lichens growing on bark or stones and observe the 

 following points : 



1. Color of upper and under surface. Moisten lichens and 



note any change in color. What gives the peculiar color 

 to lichens ? Does the composition of the compound 

 plant explain its peculiar color ? 



2. The form of lichens. Observe with hand lenses the lichens 



on bark, rocks, etc. Do you find different kinds, or 

 species, of lichens recognizable by differences in size, 

 color, and form? See the kinds of lichens on the 

 display table. 



3. Draw one or two lichens to illustrate their form. 



4. Note the fruit cups, or apothecia, on the surface of some 



of the lichens. These cups (Figs. 156 and 157 of the 

 text) are formed of spore sacs (asci) which bear spores 

 of the fungus partner of the lichen. Draw apothecia 

 to show their form and distribution. 



5. Structure of the lichen. Moisten a small piece of a lichen 



thallus and tear in pieces in' a drop of water on a slide. 

 Cover and crush out under a cover glass. Observe the 

 fungus hyphse and the algse which compose the plant 

 body. 



a. The algae. Note their form, color, and relation to the 



fungus hyphte. The latter grasp the algae with mi- 

 nute branches and absorb food from them. Are the 

 alga? multiplying by division ? 



b. TJie fungus portion of the lichen. Observe the hyphae of 



the fungus. What is their structure? Draw the 

 algae and fungus mycelium comprising the lichen. 



6. Summary. Summarize the work of the two partners, the 



fungus and the alga, in the life of the lichen. 



