258 THE TEACHING BOTANIST 



III. The Lichens 



8 1. What is the structure and ecology of the Par- 



melia, a typical Lichen ? 

 Answer as for the earlier groups. 



82. From your various sources of information, con- 



cisely describe: 



(1) the range of habitat in Lichens ; 



(2) of color; 



(3) of size; 



(4) of shape ; 



(5) of texture. 



83. Prepare a synoptical essay, of not over three 



hundred words, on the Natural History of the 

 Fungi and Lichens, emphasizing their ecology. 



Materials.- -The common Parmelia growing upon trees 

 everywhere is excellent, and both thallus and apothecia may 

 be obtained at all seasons. The students, of course, should 

 collect it for themselves, and describe it as it appears in 

 its native situation. 



Pedagogics. As in the preceding. The group is of great 

 interest on account of the remarkable symbiosis of the Algae 

 and Fungi, which should all be made plain. 



To show properly the two elements of the thallus, and 

 especially to show the spores in the apothecia, students' scalpel 

 sections are not alone sufficient, in which case they may be 

 shown how to section in pith with a razor (described in 

 Strasburger and Hillhouse, " Practical Botany") ; it is much 

 better to let them do this sectioning than to have it done 

 for them. Prepared microtome sections are very useful also. 



