THE FUNGI. 143 



dense fungal tissue which corresponds to a cortex ; inside 

 this is the green, gonidial layer, extending completely 

 around the stem ; inside the gonidial layer the fungal tis- 

 sue becomes looser ; in the center of the stem the fungal 

 tissue again becomes dense and of a more or less reddish 

 color. Repeat the observations on sections of alcoholic 

 material. 



Remembering that all green, chlorophyl-bearing plants 

 require the sunlight, is the position of the Protococcuslike 

 algal constituents, as observed in the foliaceous and fruti- 

 cose Lichens in this and the preceding section, favorable 

 for their healthy development ? Remembering that these 

 Algae require moisture for their growth, is their envelop- 

 ment in the tissues of the Fungus favorable for their 

 development ? 



5. Treat sections, not passing through apothecia, of 

 foliaceous and fruticose Lichens with iodine solution. Do 

 you find any indications of the presence of starch in the 

 fungal portions ? In the algal portions ? 



6. In the Lichens thus far studied the algal constituents 

 have occupied a definite position separated from the fun- 

 gal constituents. Such Lichens are called 

 heteromerous. In certain gelatinous Li- 

 chens the algal constituents are scattered 



without definite arrangement throughout 

 the thallus. Such Lichens are called homoi- 

 omerous. Make and examine sections of 

 such Lichens, which may be found in moist 



T , i T -i i FIG. 82. Collema 



locations on the ground and on rocks. puiposum, age- 

 (See Fig. 83.) Treat with iodine and latinous Lichen, 

 with Schultze's solution. 



7. Make vertical sections through the apothecia of 

 Usnea barbata. Sections cut in paraffin from material 

 fixed in picric acid or corrosive sublimate, stained in 

 hsematoxylin or fuchsin, and mounted permanently in 



