249 OLAF GALLØE 
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: — 
Epiphyllous | Earth- ice Rock-lichens 
| Bark-lichens lichens | 
Tropical Africa. ...... | 498 (65 %o) | 24 (3.2%) | 45 (5.8 %) | 182 (24 9/9) 
Bay | 508 (32 %o) 3 (02%) | 275(17%) | 729 (46 %) 
Denmark Pme 165 (39 9/0) | — | 86 (20 %o) 169 (39 9/9) 
feelande LE AND SENE 59 (15 %) | = | 121 (86%) | 157 (47 %o) 
| | | 
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 yet hardly beyond the very rudiments as 
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 size 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 
