178 MINNESOTA BOTANICAL STUDIES. 



plants are excluded from the present formation. Indeed, Cla- 

 donias were almost entirely absent from the present formation, 

 though the Cladonia society named above was fairly well devel- 

 oped on more horizontal rocks a few rods away. It is needless 

 to say that these two lichen societies also grade into each other 

 in the most confusing manner in some areas. 



Some of the plants of the formation seem, in the region at 

 least, to belong indifferently to the trees or to the rocks. These 

 have been designated (?) in the above list. As may be inferred 

 from statements above, tension lines are very apparent between 

 the present formation and others of the surrounding earth and 

 rocks, and it is a noticeable fact that the wandering of lichen 

 floral elements is almost always from trees to the shaded rocks. 

 In this region, devoid of limestone, Pannaria languinosa (Ach.) 

 Kbr. is frequently present in such formations and was fre- 

 quently seen in other similar formations near by and elsewhere. 



If we compare again the present formation with the similar 

 one at Granite falls, even though the trees surrounding the 

 former are partly coniferous and the latter hard-woods, we note 

 almost as much similarity in the two remote societies as was 

 seen in the exposed rock formations of the same localities. 

 No special mention need be made of the resemblances, as a 

 glance at the two lists will reveal them forcibly enough. One 

 striking difference, however, is the absence of the Endocar- 

 pons, Verrucarias and Staurotheles. If present, they were for- 

 gotten in the special study and not collected on the spot because 

 abundant at the water's edge a few rods away. Moreover, we 

 are now in a lake region where these plants, if in the present 

 formation at all, would be there by chance and out of their 

 more natural habitat on the moist rocks at the shore line. They 

 will be found recorded below in what we have seen fit to desig- 

 nate the amphibious angiocarpic wet rock lichen formation^ 

 better studied at Tower. 



Passing to the matter of adaptations, they may be summed 

 up shortly. The plants are larger forms than those of the first 

 formation above and as a rule have well-developed cortex on both 

 sides of the foliose thallus. Many of them are plants which 

 may grow on trees or earth and in less shaded stations, and the 

 society is by no means so strictly lithophytic as the one of the 

 exposed rocks. On the whole, the Ramalinas, the Collema and 

 the Leptogiums are the most typical members of the society. 



