212 OLAF GALL0E 



expressed by means of the frequency-numbers. Therefore, properly 

 regarded, these prove to be nothing else but a diagnosis whereby 

 to identify the association in nature, in the same way as the 

 systematical description of species serves to identify the systematical 

 species. 



The frequency-number, however, affords some guidance to the 

 attainment of an idea of the physiognomy of the association. But 

 certainly much more than this is necessary. An exhaustive word- 

 description, concerning all the features which cannot be explained 

 by the frequency-number, is quite indispensable. This applies more 

 especially to the mass-occurrence of the individual growth-forms, 

 where the freqency-number is a very imperfect means of description. 



As the heath is defined here, it is defined by its characteristic, 

 dominant phanerogams. 



Instead of treating the lichens found in every single plant- 

 association already-known, I could have proceeded along other lines, 

 and have classified the lichen-associations exclusively according to 

 the characteristic lichens found in them, putting aside all accustomed 

 considerations with regard to the phanerogams. Lichenologists will 

 perhaps reproach me for not having taken this course. But I regard 

 it as fully justifiable to make use of the conceptions already familiar 

 regarding associations and to widen these by setting forth what 

 lichen-studies teach us regarding them, in addition to what we have 

 already learned from the phanerogam-studies. If I were to start in 

 a one-sided way along lichen-ecological lines, then, as a matter of 

 course, the conception "heath" could not be maintained, for no 

 mass-occurrence, no frequency-number nor any other means of de- 

 finition enables us to define the conception "heath"' liehenologically. 

 We have seen that the frequency-number for the lichens of heaths 

 ranges from to 100, consequently, a heath cannot be defined 

 by the frequency-number. Neither will it be possible to do so by 

 a statement of the abundance of lichens, nor by any other means 

 c;m the term ''heath" be defined lichenologically. 



When I maintain the conception "heath," it is exclusively a 

 phanerogamic conception which I maintain, because it is old-esta- 

 blished and because the heath is easily recognizable in nature when 

 it is defined as I have done it here (F ", o 100 chamaephytes), and 

 licc-ause, everything considered, it is more particularly the phanero- 

 gams of the heath which are of importance as regards the luxu- 

 riancv or the reverse of the lichens. 



