Fink: the lichens of Minnesota. 709 



The reconstructed table below (which leaves the numbers of 

 lichens for the substrata considered unchanged in the Minne- 

 apolis column except that for the earth lichens all calcareous - 

 earth lichens plus all earth Cladonias are omitted, treats the 

 Fayette earth lichens in the same way and also deducts from 

 the latter column all the calcareous rock lichens found on sur- 

 face exposures) gives the relative per cents for all the sub- 

 strata considered as influenced by atmospheric conditions 

 alone. 



This table simply places the per cents that would result from 

 atmospheric conditions where they may be easily compared. 

 However, by the reduction of the numbers representing earth 

 and calcareous-rock lichens to eliminate other causes, it re- 

 duces the advantage for the Minneapolis vicinity in granitic 

 rock species to a very small fraction. A somewhat larger 

 number of such rocks were examined about Fayette, and pos- 

 sibly the larger number increases the number of species of 

 lichens on them, which once established may now all be found 

 on a few of the rocks. However, if the smaller number about 

 Minneapolis is due to removal of the rocks, this argument 

 loses much of its value. This table shows the relation between 

 the wood lichens, as influenced by climate alone by per cents, 

 which has not been done before. 



I have already stated that the comparative numbers of lich- 

 ens for Minneapolis and Fayette apply for individuals as well 

 as for species. Now, it must not be supposed that earth and 

 rock lichens are comparatively common at the former place 

 because the per cents are higher. A careful inspection of the 

 tables will show that this does not follow. There are only a 

 few lichen species which may be regarded as comparatively 

 common about Minneapolis, such as most of those occurring on 

 the Saint Peter sandstone, some of the Peltigeras, one or two 

 Endocarpons, Rinodina sophodes (Ach..) Nyl., Plujscia stellaris (L.) 

 Tuck, and perhaps two or three others. I have attempted to 

 state in the list whether the species are common, frequent, or 

 rare, and it seems to me that the number of rare lichens is 

 large. This is very noticeable in the Lecanoras where only one 

 species of 15 listed is given as common. 



