1898-1902. No. 21.] LICHENS. 13 



Notes: The thallus is distinctly black only when our plant comes 

 into contact on the subtratum with another lichen of the same species 

 or another. I have however noticed it overgrowing completely some of 

 the smaller species of Polyblastia. The margin exhibits a peculiar and 

 very delicate ribbing which produces an effiguration-effect. This species 

 is also closely allied to A. calcarea, (L.) SMRFT., but it differs in having 

 a black hypothallus on occasions and in the presence of 8 spores in 

 each ascus. 



The following list includes the species recorded up to now from Arctic 

 America, Greenland, Spitsbergen and Iceland. Each name is followed by 

 one reference only, where the best available description will be found. 

 I have also mentioned, relying on the authors allready referred to for the 

 statements, as to whether the species is recorded for Arctic America 

 (Am.), Greenland (Greenl.), Spitsbergen (Spits.) and Iceland (Icel.). The 

 localities of the 'Fram"-Expedition are given after the letters E. P. S. N. 

 which stand for Expeditio Polaris Secunda Norvegica. The numbers in 

 brackets after the locality refer to the more detailed list of localities 

 which follows the systematic enumeration. It was first my intention to 

 add here a key to the genera and species of the Arctic Regions which 

 I have compiled for my own use in the form of a card-catalogue. But 

 in the end I considered this premature and I have left it for a later 

 occasion. 



