I92I. No. 7- STUDIES ON THE LICHEN FLORA OF NORWAY, 



19 



an intimate acquaintance with their natural habitats can decide many dii'ii- 

 cult questions. 



Many of them are easily arranged in two subdivisions, one with their 

 chief distribution in Western, and another in Eastern Norway. The most 

 typical lichens in the western subdivision are certain large Lobaria and 

 Sticta species, and Neplirojiia /iis/'/a/i/cii/ii. 



Lobaria lactevireiis and Ncpliroma /iisifaiiiciiiii are closely related to 

 the 'south coast lichens', but both of them are equally common along the 

 western Ijords as on the west coast, and Lobaria laciiiiata and Pcltigcra 

 sciitata are more common along the fjords. Sticta silvatica and Cetraria 

 lacHuosa are western plants, but they advance farther into continental pro- 

 vinces than the others. Sticta silvatica has been recorded from Krokkleven, 

 Numedal and Telemarken, Cetraria lacttiiosa is a North American and 

 Siberian plant which M. N. Blytt was the first to find in Norway (in 

 Telemarken). In Granvin, Hardanger, it ascends to 590 m. s. m. A map 

 merely expressing the stations recorded of suchs plants is to a certain 

 extent misleading, lor it sa^'s nothing of their frequency. In Eastern Nor- 

 way botanists have detected several stations for them, but they are not 

 common there. In Western Norway they are so frequent that anyone can 

 find them. 



The lowland lichens of the eastern subdivision are best developed on 

 deciduous trees and on chalky and slaty substratum, the lichens of our 

 eastern coniferous trees are of a more subalpine character. 



Types of eastern lowland plants are Usiiea ßorida (type, excl. of 

 U. sorediifera) and Paruiclia Acctabiiliiiii. They are rare out of the 

 Kristiania tjord district, i/s/ica ßorida is not rare at the western shore of 

 the Kristiania fjord, for instance near Larvik. It is almost restricted to the 

 Fagus region, but it also occurs on Betula. Typically eastern is Physcia 

 pitlveritletita, which is very abundant on deciduous trees in the S. E. low- 

 lands as far west as Mandai, but in Western Norway proper there are 

 only a few stations. 



More widely distributed are other eastern lichens, such as Pliyscia 

 grisca and Auaptychia ci/iaris, found though not so frequently right up in 

 our large valleys. 



Besides eastern and western lowland lichens there are also lowland 

 lichens equally common in either part of the country. We may mention 

 the large Pcltigcra horizontalis, some Stcreocaulon species, as nanum and 

 coralloides, and others. 



The most widely distributed species form the transition to the 

 subalpine lichens. In many cases it is a matter of discretion where the 

 limit should be drawn. Plants like Paruiclia furßiracca and Paruiclia 

 tiibulosa extend almost up to the tree line, but they are much less common 

 at subalpine than at lowland stations. 



