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 was 
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 (Vitui.) Mass. 
Lecanora varia (Euru.) Nyv. 
Er ew 
