660 MINNESOTA BOTANICAL STUDIES. 



more variety as to trees, 154 species were collected, though the 

 calcareous formations were entirely absent and the granitic only 

 poorly developed. The disadvantage due to absence of granitic 

 and calcareous lichen formations seemed to be more than offset 

 by the unusual richness of the formations of the tamarack and 

 the cedar swamps and the earth under the pines. As this \vas 

 my first opportunity for a careful study of these three forma- 

 tions, and the tree formations were also especially rich as well 

 there, somewhat more time was taken for the collecting at Be- 

 midji than elsewhere. However, notwithstanding the scarcity 

 of any kind of bowlders and the absence of rock exposures, 

 the Bemidji region may be regarded as one of the richest lichen 

 floral areas in Minnesota, while Henning with its greater variety 

 of substrata and favorable conditions is scarcely inferior. 



From Bemidji I passed to Thief River Falls, about 80 miles 

 to the northwest. Here I found a territory composed for the most 

 part of low flat prairie, but with good woods along the banks 

 of Red lake and Thief rivers. The trees are mostly birches, 

 poplars, oaks and elms, forming a monotonous arboreal flora 

 by no means favorable to the production of a large number of 

 lichens. Inspection of the list of species and varieties recorded 

 for this region will show that only 43 lichens were found on 

 these trees to compare with more than twice as many on trees 

 at Bemidji, and that these 43 are in general the most common 

 of Minnesota lichens growing on trees. Marshes are frequent, 

 and devoid of trees ; or having the same species as grow on the 

 higher ground, sustain no peculiar lichen species. Both granitic 

 and lime bowlders are frequently seen in the region, but they 

 are almost totally bare of any sort of plant life. Doubtless this 

 is due partly to fires which frequently run over the prairies. In 

 places pastured for several years so that fires have not occurred, 

 lichens are beginning to take possession of the rocks. Yet it is 

 difficult to explain the absence of lichens along high bowlder, 

 strewn river banks, as in certain Localities toward St. Hilaire, 

 on any supposition. It will be very interesting to note the in- 

 crease of lichen flora on the rocks of this region as the country 

 becomes settled more densely and fires are kept out. In order 

 that this may be done, I record the few lichens now occurring 

 rarely on these rocks. 



Rinodina oreina (VILL.) MASS. 



Lecanora varia (EHRH.) NYL. 



