EE —<—— 
Fink: LICHENS OF NORTHWESTERN MINNESOTA. 661 
Lecanora varia (Euru.) Nyv. var. polytropa Nyv. 
Placodium murorum (HorrM.) DC. 
Placodium elegans (Linx) DC. 
Physcia cesia (Horrm.) Nyt. 
Parmelia conspersa (EnrRu.) Acu. 
The earth lichen flora is as poorly developed as that of the 
trees and rocks, and the whole known lichen population of the 
area comprises only 78 species and varieties and is the most 
scanty yet studied in the state, except that at Pipestone, where 
trees are almost wholly absent. 
The last collecting ground was at Red lake, some 65 miles 
east and somewhat south of Thief River Falls. This area is 
about 36 miles north of the one previously studied at Bemidji 
and has a lichen community very similar. Here the only 
bowlders that gave any noteworthy results were those along the 
lake shore, and the lichens on them were, all but three or four, 
of the same species as those growing upon the adjacent trees. 
With this dearth of rock lichens the territory, probably not 
quite so thoroughly studied as the one to the south about 
Bemidji, gave only 120 lichen species and varieties. 
Compared with other portions of the state of equal size, 
whose lichen floras have been investigated, this one is some- 
what the poorest in lichens. The number collected is little 
larger than that found in southwestern Minnesota, but should 
be considerably larger, as fully one-third more time was taken 
for the collecting. The Lake Superior region gave 258 lichen 
forms in about the same time as was spent in making the col- 
lections in northwestern Minnesota. However, this is what 
would be expected since the former area is more diversified as 
to climate, the portion near the lake having many arctic and 
subarctic species, while the northern and western portions 
yielded essentially the same species as the region now under 
consideration. Then too the absence of the great exposures of 
igneous rocks of the Superior region has already been noted 
for the present one, in which only 58 species and varieties of 
lichens, or about 28 per cent. of the whole lichen flora, were 
found on rocks, whereas nearly 50 per cent. of these plants in 
the former region were collected on the rocks. The occurrence 
of about three-fourths of the entire number of lichens of the 
whole area under consideration in one small area about Bemidji 
demonstrates that little of the difference in the composition of 
