278 MINNESOTA BOTANICAL STUDIES. 



This being the most northwestern area reached in the survey, its 

 lichen flora was studied carefully. The final task was to study 

 the lichen flora of the pipestone and the Sioux quartzite at 

 Pipestone. 



A brief statement as to substrata is next in order. About 

 Mankato trees abound, and three kinds of rock — limestone, 

 sandstone and bowlders — are plentiful. I found only the two 

 interesting substrata mentioned above atNewUlm. Trees and 

 bowlders were abundant, but were not studied for the reason al- 

 ready stated. At Redwood Falls, Morton and North Redwood, 

 granite trees and earth were examined for species especially 

 rare or interesting. The great masses of granite, supposed to 

 have been exposed since the close of the glacial age, formed the 

 most interesting substratum at Granite Falls. This is also the 

 most northwestern area in the valley where trees occur in any 

 considerable numbers. The calcareous drift pebbles and cal- 

 careous earth proved also very interesting here. The two sub- 

 strata examined at Pipestone have been mentioned. I need to 

 add only one statement more to make the analysis of substrata 

 complete enough for the present purpose. This is that earth 

 was examined everywhere and furnished much of interest, as 

 wdll appear later. 



The following rare lichens were found only at Redwood 

 Falls, Morton or North Redwood : Peltigcra canina (L.) 

 Hoffm. var. sfongiosa Tuck, and Stcreocaiilon paschale (L.) 

 Fr. Also the area including the above places forms the most 

 southeastern known extension of the following lichens in the 

 valley : Pannelia olivacea (L.) Ach. var. prolLxa Ach. ; Pa7i- 

 naria microphylla (Sw.) Delis; Omphalarta phylltsca (Wc^hl.) 

 Tuck. ; Lecanora frusUilosa (Dicks.) Mass., and Biicllia ftil- 

 lata Tuck. With this much in hasty review I shall pass to lo- 

 calities more thoroughly studied. However, I may add here 

 better than elsewhere in my paper that Rinodina orema (Ach.) 

 Mass. and Lccanora xanthofhana Nyl. are here and elsewhere 

 in the valley far more abundant than I have ever found them in 

 other regions. 



In attempting a general comparative stud}^ of distribution in the 

 valley the places that present questions of greatest interest are the 

 vicinities of Mankato and Granite Falls, where all sorts of sub- 

 strata were examined. The two areas were about equally well 

 studied, though the former, because of the greater number and 



