22 OLAF GALLØE 
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” lichenologically. 
We have seen that the frequency-number for the lichens of heaths 
ranges from 0 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 
can 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 chamæphytes), and 
because, everything considered, it is more particularly the phanero- 
gams of the heath which are of importance as regards the luxu- 
riancy or the reverse of the lichens. 
