1()2 OLAF GALL0K 



Rhizocarpon petraeuiu. Verrucaria niargacea. 



viridiatrum. mucosa. 



Staurothele clopima. nijrescens. 



Verrucaria maura. rupestris. 



As regards a few of these species it is true that they not only 

 occur on common rocks, hut also on disintegrated, bleached bones 

 of various animals, usually on bones of sheep, which are ratlin 

 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 

 Umbilicarid. (iijrophora, Parmelia. etc., may be sub-divided into at 

 least two types, viz. the Gyrophora-iype and the Parmelia-(\[>e. 



The Gj/ro/;/io/'-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 Parnielia-i\pe. 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 Sc h wen dene r and others. 1 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, 



