46 BERNT LYNGE. M.-N. Kl. 



medullaire que par un tissue plus dense, in the latter species les deux 

 cortex sont en plectenchyme assez regulier. I have examined the plants 

 of ARNOLD and HARMAND, and recognize the structure of the lower cortex 

 as a sufficient distinguishing character between the two species. 



A plectenchymatous lower cortex is never found in Norwegian plants; 

 they belong exclusively to the Physcia dimidiata . (sensu HARMAND). But 

 there is a great confusion respecting the names, some authors using the 

 name dimidiata* and others the name tribacia for our species. 



I have not seen the plants of ACHARIUS, and cannot decide whether 

 they belong to the one or the other of the above mentioned species or 

 whether they represent a mixture of both of them. Parmelia tribacia is 

 absent in SOMMERFELT'S herbarium and cannot therefore be identified from his 

 plants. But there cart be no doubt that it must have been identical with 

 our species, that is so frequent in Norway, and not with the other, other- 

 wise never recorded from our country. It is also probable that SOMMER- 

 FELT'S plant was not a mixture, but the pure species, described here. If 

 therefore Lecanora tribacia ACH. should be a mixture, we can fall back on 

 the name of SOMMERFELT (1826) as the starting point for the nomination 

 of our species. 



It is evident from the description by WAINIO that his Physcia stel* 

 laris * tribacia in Adjumenta and in his Pitlekai paper is identical with ours, 

 as is also MALMES plants which I have examined. WAINIO has had access 

 to the ACHARIAN herb, in Helsingfors, and if the AGRARIAN plants should 

 not have been identical with the Scandinavian ones, he would surely have 

 elucidated the question. 



Thallus growing in middle-sized rosettes, 2 4 (5) cm. in diam., but 

 inclined to grow in dense clusters, covering larger areas; it is loosely 

 fixed to the subtratum. Laciniae more or less ascendent, at the 

 circumference slightly appressed. They are contiguous or imbricate, 

 originally narrow (0,5 i mm.), in age broader (i 2 mm.), closely imbri- 

 cate or even panniform. Laciniae multifid, repeatedly deeply incise, fur- 

 cate or pinnate with undulate or crenate contours, towards the apex from 

 slightly widened to flabelliform. The short lateral branches 

 sorediate at their apices, soredia initiating at the limit between the 

 upper and the lower cortex and at the adjacent parts of the lower cortex, 

 rarely at those of the upper side. Gradually the sorediate apices become 

 ascendant or even incurved, exposing the soredia to wind and air (facili- 

 tating their dissemination). Soredia in age expands along the margins, 

 abbreviating the laciniae and occasionally transforming them into a pulvi- 



