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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 briefly 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 Linné’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 
