Minnesota Plant Life. 469 



Mingled with the mosses there may sometimes be smah shrubs 

 or herbs. Stich moss heaths are to he found upon some of the 

 islands in Lake of the Woods and Rainy Lake. 



Lichen heaths. A related class may be described as lichen 

 heath. The characteristic plants of this formation are the rein- 

 deer mosses ; and very beautiful examples exist along the north- 

 ern limits of the state. The dry, rounded, thin-soiled islands 

 in Lake Saganaga give perfect examples of lichen heaths. A 

 few trees and shrubs are present, but the characteristic and pre- 

 dominant vegetation is composed of reindeer mosses with 

 little heaths, grasses, rushes, verbenas, and vetches mingled with 

 them. 



Shrubby heather. Another class not so extensively repre- 

 sented in Alinnesota as elsewhere is the shrubby heather, in 

 which the ground is covered by little heath bushes, mosses, 

 club-mosses and junipers. Yet such heaths to a limited extent 

 exist in the northern part of the state. Mingled W'ith the heaths 

 proper are a number of composites, such as those goldenrods, 

 asters, and fleabanes wdiich prefer dry open localities. 



All of these rock and heath groups of plants are strongly 

 xerophytic in their general features. They are, in many in- 

 stances, to be regarded as responses to sterility of soil rather 

 than aridity of climate. 



Sand plants. \'ery closely connected with rock vegetation 

 is the sand vegetation of dunes, beaches and barrens. The sand 

 is lacking in moisture, which percolates through it readily, 

 lacking also in nitrogenous substances and, therefore, to some 

 degree not unlike a rock tract, hence naturally presenting 

 similar types. A great many plants which can grow^ upon rocks 

 can also grow upon sand dunes and, as a result, in the northern 

 part of the state, junipers, for instance, occur in about equal 

 frequency upon bare rock ledges and upon sand dunes. A 

 special type of sand vegetation is that of sandy beaches, where 

 the proximity of lake water makes the soil moister than it 

 W'Ould otherwise be. For this reason the plant inhabitants of 

 beaches are often mesophytic rather than xerophytic in char- 

 acter, while close to the water's edge true hydrophytes may 

 establish themselves. Dunes are particularly characterized by 



