96 Minnesota Plant Life. 



of little circular discolored patches found on bowlders and cliffs. 

 In the centre of such a discolored patch are scattered the irreg- 

 ular-shaped fungus fruit-bodies, in which are produced numer- 

 ous spores incapable of germination. In rock-lichens of this 

 sort the fruit-bodies are not exactly circular, as in the majority 

 of the grouj). The algae which are present are of rather higher 

 types than in some of the more complicated lichens. They be- 

 long to the class of bright-green algae, and sometimes branched, 

 filamentous algae are found in the partnership, while at other 

 times isolated green-slime cells are the rule. 



Rock-lichens. The majority of rock-lichens in AUnnesota in- 

 clude bright-green algae rather than blue-green, and the fungus, 

 when it fruits, produces a circular disc, reminding one exactly 

 of many of the cup-fungi. The centre of the disc is often va- 

 riously colored, red, black, yellow, blue, purple, pink or dull 

 green. The texture, too, of the lichen-body differs in different 

 kinds, for in some it is papery and thin, while in others it 

 may be brittle and encrusted. Again it may be leaf-like, or 

 gelatinous. In addition to the closely attached forms growdng 

 upon rocks are certain loosely attached varieties — one very con- 

 spicuous species being held by a delicate stalk at the centre, and 

 then spreading out into a round flat structure the size of a pond- 

 lily leaf and much resembling a piece of leather. Related to 

 this form on rocks is a kind which is common among mosses, 

 producing a broad green, leaf-like expansion, but it may easily 

 be recognized as a lichen if it is turned over to reveal the white 

 fungus-like appearance of its under side. 



Reindeer-mosses. Most remarkable of the lichens is the 

 reindeer moss wdiich is so predominant a form of vegetation in 

 polar regions. There are a large number of different species 

 and for the most part they grow upon the ground. Reindeer 

 moss in Northern Minnesota often forms patches of hemispher- 

 ical shape and as large as a bushel basket. Plants of this size 

 must be very old, possibly over a hundred years, for they grow 

 slowly and are of perennial habits. I have seen them most 

 beautifully developed on an island in Lake Saganaga, where 

 they covered the soil among the pine trees and I could not help 

 remarking that they seemed to be as old as the pine trees above 

 them, indicating what is rare in Minnesota, that the island had 



