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OLAl C.ALL0E 



in the Tropics, better in the Sub-tropics, better still in the Temperate 

 countries, and best of all in the Arctic countries and in Iceland 

 as regards conditions concerning competition. The climate, on the 

 other hand, appears to be directly unfavourable to them in the 

 Arctic regions and in Iceland. 



This is best shown in a Table: 



Bark-lichens 



Earth-lichens Rock-lichens 



These figures have been commented upon more fully in the 

 above, both the actual figures and the percentages. 



But the other side of the matter still remains to be discussed, 

 viz., the valuation of the wealth of the various regions as regards 

 the mass-development, as far as this is manifested by frequency 

 numbers and masses (given in weight per unit of area). Hitherto 

 we have been exclusively dependent upon a superficial valuation 

 of this, and we are as vet hardly bevond the very rudiments as 



*//*. fc 



regards this point, but it need not continue to be so in the future. 

 I shall record here the little that is known and may be discerned, 

 but, firstly I shall dwell a little on the precautionary measures 

 which must necessarily be taken in order to be able to judge some- 

 what correctly. 



The cause which chiefly leads us to judge erroneously, is the 

 fact, that we are involuntarily deceived by the sixe of the phanero- 

 gams compared with the lichens. Thus, we may very easily be 

 struck by the abundance of lichens on mountain heights, in places 

 where phanerogams are either totally or almost wanting, and on 

 the other hand, underrate the abundance of lichens where the larger 

 phanerogams are more numerous. This is in itself so common and 

 significant a source of delusion when forming an estimate of the 

 abundance of lichens, that as a rule we must be very cautious about 

 relying on the results which the botanist in question puts forward, 

 if we do not know beforehand his conception of this circumstance. 

 But even if the botanist happens to judge quite correctly, yet he 



