STUDIES ON THE VEGETATION OF ICELAND 161 
ane knolly m6 ..:....... 6.8, 6.8, 6.4, 6.2 average 6.5 
LUI RS OR ere 6262 6:15 6.1 — -6.2 
OT) eee eae G2, 64, 60: 5949-56 — 59 
Geiri (Geranium belt)... 6.5, 64 — 6.3 
— (bottom veget.).... 6.3, 6.1 _ 
Thus the Icelandic soils all seem to be slightly acid; no degrees 
of acidity above the neutral point were measured, nor did any very 
strongly acid soils occur. The highest value measured in py was 
6.9, the lowest 4.8; according to C. Olsen, the corresponding values 
for Denmark are respectively 8.0 and 3.4. There is this connection 
between the moisture of the soil and its degree of acidity that in- 
creasing moisture produces increasing acidity, i. e. decrease in py 
value. In melar py is about 6.7, in the mo 6.3—6.5, in jadar 6.0— 
6.2, and in myri 5.2, 5.5, and 5.9. An increase in the depth of 
snow-covering shows the same relations: in melar p" is 6.7, in mo 
6.3—6.5, and in geiri 6.1—6.3. | 
The investigations described in the present treatise are not only 
of phytogeographical and botanical interest, but would also seem 
to have some bearing on practical matters, partly in agricultural 
research, and partly more directly in farming. Since, however, 
these matters have not been subjected to special investigation and 
are outside the scope of the present treatise, I shall merely make 
brief mention of a couple of questions connected herewith. 
Under the treatment of the vegetation the appearance of the 
surface in the individual types was described. A comparison be- 
tween this and the species group spectra reveals the following facts. 
When the E percentage is high, i. e. when the vegetation 
consists of southern species, the surface is always level, 
without any formation of knolls, whether the high E per- 
centage is caused by a deep layer of snow or by the soil being 
covered with water. If, reversely, the vegetation consists 
mainly of arctic species, solifluction is always seen. If 
the vegetation consists of an equal mixture of A and E 
species knolls will always be met with. 
This difference between the types of surface connected with 
the different types of vegetation must be assumed to be a result of 
the same external factor that determines the differences in vege- 
tation, in this case the cold. In geiri and flöi (snow-patch and 
The Botany of Iceland. Vol. IN. 11 
