674 MINNESOTA BOTANICAL STUDIES. 
found during that summer at least belong to living or to dead 
wood formations though occasionally the plants on dead wood 
may persist after the wood has begun to decay perceptibly at 
the surface. 
The lichens of this formation are of the small, closely adnate 
or hypophceodal crustaceous type with upper cortical protection 
in the Lecanoras and Placodiums and none in the Arznodina, 
the Lecidea, the Buellias and the Caliczums. The substratum 
is a dry one usually, as I have not concluded the more damp and 
more frequently rotting logs of the tamarack swamps, which 
have their own peculiar formation recorded below. Hence, the 
crustaceous type of thallus is especially adapted to the forma- 
tion. True the Calczums put up the minute erect podetia, but 
these are solid cylinders of hyphe running in a longitudinal 
direction and usually quite devoid of the algal symbionts which 
might suffer from dryness. 
The last of the formations to be compared with those studied 
in 1897 in southwestern Minnesota is the following. 
CLADONIA LICHEN FORMATION OF ROTTEN WOOD (BEMIDJI). 
Peltigera canina (L.) Horrn., C. 
Peltigera canina (L.) Horr. var. sorediata SCHAER. 
Cladonia mitrula Tuck. 
Cladonia pyxidata (L.) Fr. 
Cladonia pyxidata (L.) Fr. var. neglecta (FLK.) Mass. 
Cladonia fimbriata (L.) Fr. var. tubeformis Fr., C. 
Cladonia fimbriata (L.) Fr. var. simplex (WEts.) FLor. 
Cladonia gracilis (L.) Nyt., C. 
Cladonia gracilis (L.) Nyu. var. hybrida ScHaErR. 
Cladonia gracilis (L.) Ny. var. symphycarpia Tuck. 
Cladonia gracilis (L.) Nyv. var. verticillata Fr., C. 
Cladonia gracilis (L.) Ny. var. anthocephala Fix. 
Cladonia macilenta (EHRH.) HorrM. 
Cladonia bacillaris Nyt. 
Cladonia cristatella Tuck. 
Comparing this formation with the corresponding ones at 
Mankato and Granite Falls,* we find that the formations are 
constant at least as regards genera, the one herein recorded for 
a region, especially rich in C/ladonzas, being of course richer in 
species than the two formerly studied. The addition of a third 
7 Bink. Be 1es,)306—-307. 
