135 
is the age-relationship, from a purely Arctie (Alpine) point of 
view, which exists between the four above-mentioned species, 
but I am inclined to believe that the species of Cassiope are 
the oldest in that respect. 
The leaves of the deciduous forms scarcely suggest an 
Arctic climate. They are all built more compactly than are the 
leaves in the forms especially mentioned by Bércesen (1895); 
but then it must be remembered that they occur also in moor- 
land soil or at any rate in sour, peaty soil. Of these forms 
only Vace. uliginosum is common in the Arctic regions. Ana- 
tomically it hardly differs from the southern forms. Judging 
especially from the fact of Arctostaphylos alpina having larger 
intercellular spaces it is doubtless less xerophytic than is 
Vacc. uliginosum. Vace. Myrtillus is scarcely sufficiently old- 
established in the Arctic regions to be referred to the Arctic 
Flora. 
Among the cases in which I have investigated the leaves 
of southern specimens, only rarely have | been able to prove 
that a lessening of the palisade-tissue accompanies further 
advance southwards into the lowlands. But then it must be 
remembered that the material has not in any way been com- 
plete. In regard to the slight difference observed in the xero- 
phytic structure of the North-European and of the Arctic 
individuals of the same species, this may possibly — only 
possibly — be due to the fact that winter-time, the most 
dangerous time of the year, the time when evergreen leaves 
need the greatest protection, does not in many points differ 
greatly in the localities in question. 
All the species described in the present paper have tannin 
in their leaves; most likely it is a family characteristic which 
is useful to them in the Arctic regions. In some Danish and a 
few Arctic specimens I have seen the plasma and the chloro- 
phyll-contents of the evergreen leaves in the winter condition 
