4898—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.) Smrrv., 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 ir 
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. 
