Fink: lichens of the northern boundary. 181 



A noticeable difference between the present list and those for 

 the two areas named above is the omission of the Pcltigcras from 

 the present one. Both of the forms of the genus recorded in 

 the previous reports were seen frequently enough at Emo and at 

 other points where the formation was noted with less care, but 

 they were seldom seen on rotten wood. Some of the apparent 

 difference in the three lists as to the forms of Cladonia is due to 

 the adoption of Dr. Wainio's nomenclature, but Cladonia squa- 

 mosa (Scop.) Hoffm. and the two forms of Cladonia -pityrea 

 (Flk.) Fr. are additions. The last lichen of the above list is a 

 species not known farther south, as is also the Cladonia named 

 last above. Inspection of the three lists will show that there is 

 more than the usual amount of variation in these formations in 

 different regions. The adaptations have received sufficient at- 

 tention in the sixth report. 



Passing now to the swamp formations, we may best record 

 two that are somewhat closely related and sometimes confusingly 

 intermingled. These are the formations of the tamaracks and 

 those of the cedars of the swamps. The first recorded below 

 was studied at Henning and the second at Bemidji, and the 

 formations as observed at those places have been recorded in 

 the sixth report of this series. 



Usnea Lichen Formation of Tamaracks in Swamps 

 (Beaudette). 



Cetraria ciliaris (Ach.) Tuck. 



Cetraria juniperina (L.) Ach. var. pinastri x\ch. 



Evernia prunastri (L.) Ach. 



TJsnea barbata (L.) Fr. var. florida Fr. 



Usnea barbata (L.) Fr. var. ceratina Schaer. 



Usnea cavernosa Tuck. 



Alectoria jubata (L.) Tuck. var. chalybeiformis Ach. 



Parmelia physodes (L.) Ach. 



Parmelia olivacea (L.) Ach. 



Physcia hispida (Ach.) Tuck. 



Ramalina pusilla (Pre v.) Tuck. 



The above formation was studied on a few tamarack trees of a 

 swamp some distance from Beaudette along the railroad that was 

 being surveyed during the summer and on the Canadian side. 

 The trees were surrounded by cedars, and most of the lichens 

 of the above list were found on the cedars also. In short, most 



