132 OLAF GALL0E 



defined patches, the so-called sorals. They have been regarded 

 partly as a peculiar means of propagation produced recently, from 

 a phylogenetic point of view, in the more differentiated (little pri- 

 mitive) species, partly as a pathological phenomenon, due to the 

 fact that the gonidia, with abundant moisture, grow "wild," and burst 

 the outer morphological frame, which the lichen-hyphae would give 

 to each species, as the one characteristic to the species. 



That soredia-production may be pathological, and in many cases 

 is exclusively so, I lake for granted, but I am equally convinced 

 that it is not so in all cases. Because in that case, Cladonia pityrea, 

 for instance, which is always sorediiferous, must be regarded as a 

 pathologically deformed form of another species, which, under normal 

 conditions, has a quite different appearance. Something to that effect 

 we were obliged to assume as regards the many other lichens, 

 entirely or partially covered with soredia, which occur all over the 

 world. But that such a view cannot be maintained, I consider as 

 certain. It must, however, be pointed out that cultural experiments 

 alone, can decide this question, and such experiments have not been 

 made. It would be necessary, for instance to cultivate soredia in 

 a place drier than that where the sorediiferous species in question 

 has been collected, and try if such a culture would produce a totally 

 different, non-sorediiferous individual, which might, perhaps, prove 

 to be a species already known. Whether soredia-production is a 

 pathological or a normal feature, at all events there is no doubt 

 that it is promoted by dampness. 



Soredia have also been regarded as a normal means of pro- 

 pagation in the species in question, and there is no reason what- 

 ever to doubt that they may be of this importance. In itself there 

 is nothing to prevent soredia-production from being in some cases 

 pathological, in others normal. 



In the Crustaceous Lichens of Iceland soredia-production 

 does not appear to be a common phenomenon. I did not find it 

 widely distributed. Lepraria appears to be much less widely dis- 

 tributed in Iceland than in Denmark. Among the Folia ceous 

 Lichens, soredia-production is met with in Cetraria saepincola v. 

 chlorophylla, Parmelia ambigua, incnrva, physodes, saxatilis, stygia, 

 Physcia ccesia, obscura and stellaris. 



Among the Fruticose Lichens it is found in several Cladonia 

 species (Floerkeana, pityrea, fimbriata, etc.), Kamalina subfarinacea 

 and Usnea mela.vantha. In several of these species soredia appear 



