STUDIES ON THE VEGETATION OF ICELAND 35 
10. The Grimmia Heath Vegetation. 
11. Grassland. a. Grass slopes, b. knolly grassland (græsmo), 
c. dry uncultivated grassland without knolls (valllendi), d. the 
homefield ü(tn). 
12. Heather Moors. 
13. Willow Copses. 
14. Birch Copses and Birch Forests. 
The principles on which the above classification has been based 
take account partly of environment and partly of purely phy- 
siognomic features. If, however, a biological point of view is adop- 
ted, it will be natural to continue according to the principles em- 
ployed above in the division of the Icelandic zones of altitude. 
In Ingimar Oskarsson’s paper on the vegetation and flora in 
Vestfirdir all the species noted are given under each type of vege- 
tation, and for each species its upper and lower limit. Table 8 
below has been worked up from these data and gives both the 
spectra of the species groups and the biological spectra of the indi- 
vidual altitudinal zones for the whole area and, finally, for the 
individual types of vegetation. 
With regard to the altitudinal zones the table shows a steady 
decrease in the number of species from below upwards. The bio- 
logical spectra show a H percentage which is practically constant 
throughout all zones, but a steadily increasing Ch percentage and 
steadily decreasing Th, HH, and G percentages from the lower 
towards the upper zones. The corresponding change in the spectra 
of the species groups is an increasing excess of A, especially A 3, 
species, and a steady decrease of E species, the E1 species dis- 
appearing first, the E4 species last. All these facts are thus in close 
agreement with those stated for the whole country. — Only the po- 
sition of the 20 p.c. Ch biochore forms an exception since it lies 
considerably lower here. 
The vegetation spectra have apparently a very variegated ap- 
pearance. It is, however, possible to combine them to form several 
characteristic groups. Thus one group comprises the series melar 
— mo — herb flat, in which the melar vegetation has the highest 
A percentage and the lowest E percentage. The reverse is the case 
with the herb flats, while the mo occupies an intermediate position. 
Another group consists of the melar — mo — myri and fresh- 
water vegetations. Here the difference is that the melar has the 
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