Minnesota Plant Life. 



95 



development, for clearly the problem of obtaining illumination 

 is much the same for a lichen-partnership that it is for an inde- 

 pendent moss or fern. 



Lichen-fungi. The kinds of fungi which have formed a habit 

 of entering such lichen-partnerships are as various as the species 

 of algae. There are among them a few stalk-fungi, related 

 somewhat to the mushroom group, and when these fungi bear 



FIG. 37. A lichen growing upon a rock, and covered with the characteristic saucer-shaped 

 fruits of its fungus component. After Atkinson. 



fruit, in the lichen-partnership, they produce their spores on 

 stalks in groups of four just as the mushroom does. Most of 

 the lichen-fungi are, however, sac-fungi, a few of which could 

 be classified among black fungi, but by far the greater number 

 in the group of the cup-fungi and the disc-fungi. 



Kinds of lichens in Minnesota. There are probably some 

 500 species of lichens in Minnesota, and the total will rather 

 exceed this estimate than fall below it when the work of dis- 

 covery is completed. Among the simpler forms are a number 



