LICHENOLOGY OF ICELAND 107 



individual range of variations, which is the reason that the boundary 

 line between the species, is difficult to distinguish. 



But this is, at present, mere assumption, and as such will not 

 be discussed here more fully. I shall only remark, that any certain 

 decision on the matter can only result from making experimental 

 cultures with the types along the lines, on which researches on 

 heredity are now carried out. But unfortunately we have far to go 

 before we reach this stage, for lichens are generally very difficult 

 to cultivate and, in addition, grow very slowly, so that they would 

 not give quick results. 



This best mode of separating the species the experimental 

 mode will perhaps never be followed by any one. The next- 

 best method which, indeed, must form the introduction to the 

 experimental method has not been adopted to any extent by 

 lichenologists. I shall now brielly explain what I mean. 



In order to be able to decide how many types (species) there 

 exist, it is absolutely necessary to follow quite another method than 

 that hitherto followed by lichenologists. From the infancy of lichen- 

 ology up to the present time, the systematists, dazzled by Linne's 

 short, emphatic diagnosis of higher plants, have endeavoured to 

 create a similar diagnosis for the lichen-species. Anything like this 

 is however impossible, and has caused the greater part of the 

 systematic chaos in which we now find ourselves. If we bear in 

 mind what I wrote above on the abundance of the intermediate 

 forms, and the absence of corresponding boundary lines, it is self- 

 evident that each single type must be described and figured as 

 exhaustively as possible, in order to be recognized by other 

 workers. 



The only sure means of making a type recognizable for others 

 is to examine, figure and describe one single individual 

 of the type, making sure that we do not unintentionally confuse 

 two nearly allied types together in one mixed description, as for 

 instance might happen through investigating the thallus of one 

 specimen and the apothecium of another. 



This method, which has as yet never been practised in works 

 on lichen-systematology, (I myself have, however, material in hand, 

 not published, for some type-descriptions of such a kind), will be 

 the only means of distinguishing the types from each other, and 

 of eventually forming an introduction to culture-experiments, (which 

 as already mentioned must begin with well-defined types), so that 



