132 OLAF GALLOE 
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-hyphæ 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 take 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 Foliaceous 
Lichens, soredia-production is met with in Cetraria saepincola v. 
chlorophylla, Parmelia ambigua, incurva, physodes, saxatilis, stygia, 
Physcia cesia, obscura and stellaris. 
Among the Fruticose Lichens it is found in several Cladonia 
species (Floerkeana, pityrea, fimbriata, etc.), Ramalina subfarinacea 
and Usnea melaxantha. In several of these species soredia appear 
