162 OLAF GALL®E 
Rhizocarpon petræum. Verrucaria margacea. 
— viridiatrum. — mucosa. 
Staurothele clopima. — nigrescens. 
Verrucaria maura. — rupestris. 
As regards a few of these species it is true that they not only . 
occur on common rocks, but also on disintegrated, bleached bones 
of various animals, usually on bones of sheep, which are rather 
commonly found lying out in the open air. With regard to this 
point further particulars will be found in the table of the chief 
biological conditions of the different species. 
The Foliaceous rock-lichens. The numerous species of 
Umbilicaria, Gyrophora, Parmelia, etc., may be sub-divided into at 
least two types, viz. the Gyrophora-type and the Parmelia-type. 
The Gyrophora-type (Gyrophora, Umbilicaria), as we know, con- 
sists of lichens which are attached to the substratum at a single 
point on the under surface of the thallus — the “umbilicus”. This 
is the reason why the lichens cannot die away in the centre and 
form “fairy rings.” With regard to absorbtion of food from the sub- 
stratum, such species are differently conditioned from the Parmelia- 
like-lichens which are attached to the substratum at various points. 
With regard to capacity for competition, all the species stand very 
high, as they very easily grow across their competitors. Hence, in 
many places in Arctic regions, they form, on the rocks, growths 
very conspicuous and rich in individuals. 
The Parmelia-type. Its many species are attached to the sub- 
stratum by numerous rhizines, and die away in the centre, forming 
“fairy rings,’ without thereby losing their foothold. This feature is 
very commonly seen in Parmelia saxatilis. 
The ordinary anatomical structure has already been long known 
from the investigations of Schwendener and others. | shall only 
draw attention to the fact that there are cortical layers on both 
sides, as also a gonidial and a medullary layer. 
The morphological structure still requires much investigation, 
especially from a biological point of view. 
The means of propagation are, in addition to ascospores, in 
some species soredia also. How widely distributed the latter are, is 
not known. Propagation by means of detached portions of thallus, 
does not appear to have been observed in any of the species. 
In competition the foliaceous lichens are far superior to the 
crustaceous lichens, when the substratum has, in some measure, 
