214 OLAF GALI.ui-: 



associations, and some by others on Icelandic soil without closer 

 notification of the association. There is hardly a single Icelandic 

 earth-lichen which avoids the heath: they certainly all occur there 

 occasionally, although those enumerated in the above list doubtless 

 form the nucleus of the lichen-vegetation of the heath. 



As may be seen, there have been found 9 fruticose podetia- 

 wanderers, 6 fruticose hypothallus-wanderers, 3 erect and 8 procum- 

 bent foliaceous lichens, and 19 crustaceous lichens. 



But, as already mentioned, to these must probably be added 

 all the other earth-lichens, viz. 12 fruticose, 1(5 foliaceous and 48 

 crustaceous species. 



It is much to be desired that we could compare the lichen- 

 vegetation of the Icelandic heaths with that in other countries, for 

 instance in Denmark. Our knowledge of the lichens from heaths 

 in other parts of the globe, is practically nil. As we know, lichen- 

 ecological observations have, up to the present date, played a very 

 subordinate part in scientific work. 



Some of the most conspicuous points which there could be 

 reason to compare are the agreements or disagreements as regards 

 (1) systematic species, (2) growth -forms, (3) frequency -degree and 

 (4) mass-occurrence. 



With regard to systematic species there is a very conspicuous 

 difference between the Danish and the Icelandic heaths. Whilst the 

 Danish heaths - - as far as they contain lichens at all - - are entirely 

 dominated by Cladonia ranyiferina, the Icelandic heaths are not 

 dominated by any single species. It is true, reindeer moss occurs, 

 but only in small quantities. Of far more frequent occurrence 

 are Alectoria ochrolenca, Thamnolia vermicularis, Cetraria islandica 

 and Lecanora tartarea. Thus the Icelandic heaths cannot be cha- 

 racterized by any single species. We shall not, however, go further 

 into details as regards the systematic species, it will suffice to refer 

 to the list of the Danish Heath-lichens in "Danske Licheners 0ko- 

 logi" (p. 305) and, as regards the Icelandic lichens, to the list of 

 species given above. 



The growth-forms are not exactly the same on the heaths of 

 Iceland and Denmark. Whilst Denmark has 21 fruticose lichens 

 .~>7 /o of the heath-lichens), 3 foliaceous lichens (8 %>) and 13 cru- 

 staceous lichens (35 %), in Iceland the proportions of growth-forms 

 are distributed as follows:- 15 are fruticose lichens (33 %), 11 are 

 I'oliaceous lichens (24.5 /o), and 19 are crustaceous lichens (42 %). 



