l.'M 01. AI (i.M.I.OK 



Species such as Cladonia ranyiferma, Alectoria ocliroleuca, Celrnria 

 (icnleata, and Alectoria nigricans are undoubtedly far more frequently 

 propagated by detached portions of thallus, some carried away by 

 the wind, and others adhering to the body of animals. 



That portions of thallus should be able to pass through 



the digestive organs of animals uninjured, is a priori improbable, 



if such were the case, they would be rather useless as fodder! 



Any possibility of such dispersal by means of herbivorous animals, 



is thus scarcely possible. 



But water, also, plays a part in the dispersal of lichens. By 

 the agency of water, the submerged Verrucaria spp. which live along 

 the coasts, are undoubtedly dispersed. Then it is probable that the 

 lichens which occur by water-falls, part of which live washed by 

 the falling water (for instance Staurothele clopima), are dispersed 

 by the downward-flowing water. 



If we now consider the agencies which play or have played a 

 part in the exchange of lichen-species with the surround- 

 ing countries, we must, as in the case of dispersal in Iceland 

 itself, point out three different agencies: wind, water and animals. 



The lichens which may be assumed to have immigrated, (re- 

 spectively emigrated,) by the agency of the wind, are firstly all 

 those that propagate by ascospores, consequently, practically all 

 the crustaceous lichens, at any rate, by far the greater part of the 

 species (about 65 %); then next, the majority of the foliaceous lichens, 

 possibly all of them (there are altogether about 21 % of them); and 

 lastly some fruticose lichens. As regards the latter, however, it must 

 be taken for granted, that at least Thamnolia vermicularis did not 

 migrate in the form of spores, as it never bears fruit. 



Some of the species have probably also migrated by means of 

 pycnoconidia, but as the occurrence of the latter in the species 

 is very incompletely known, and as their importance as a means 

 of propagation may be disputed, it is not possible to form any 

 opinion as to what importance they are of or have been, in respect 

 to immigration. 



Lastly, some species have migrated as soredia. As mentioned 

 above the soredium is not a very common means of propagation 

 in the Icelandic species; in the crustaceous lichens it is extremely 

 rare. I am not prepared to state with any certainty in how many 



