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STUDIES ON THE VEGETATION OF ICELAND 163 
By the investigations described in the present treatise it has 
been shown how, within 3 areas in normal Icelandic physical con- 
ditions, favourable conditions for southern species are created, and 
thus a vegetation, the luxuriance of which permits of grazing or 
haymaking. These areas are either soils protected by water or by 
snow, or moderately moist soils which combine the favourable 
temperature conditions in winter of moist soils with the favourable 
temperature conditions in summer of dry soils. 
The value of these areas for farming is caused by the fact that 
southern species and life-forms are larger and more vigorous, pro- 
duce more matter than northern ones. Hence one of the chief 
aims in cultivating infertile areas should be to make such changes 
in the prevalent external factors that from being favourable to Ch 
they become favourable to H or G, according as the soil to be cul- 
tivated is comparatively dry or comparatively moist. The means 
employed for this purpose have been, partly a change in the con- 
ditions of moisture, partly in the conditions of nutrition. The re- 
sults have, however, been very varied. The experiments have been 
most successful in the case of myri, which it has been attempted 
to eultivate partly by irrigation, partly by draining. It is obvious 
that irrigation must result in favourable conditions for southern 
plants, since it increases the medium of protection against the winter 
cold. If the water is drained off in the summer, this will merely 
be a further advantage, since a lot of heat which would otherwise 
be latent in the water now becomes available for the plants. As a 
matter of fact, the transformation of myri into irrigated myri plays 
a prominent part in Icelandic farming. 
The second way in which myri may be transformed is by 
draining. In that way moist soil is transformed into moderately 
moist soil, myri to tin. This change in moisture in connection 
with the addition of manure will have the efffect of gradually re- 
placing the sedge vegetation of the myri, rich in G, by the grass 
vegetation of the tin, rich in H — a vegetation identical with the 
jadar vegetation. Thus draining also produces a more southern 
vegetation, and the causes have previously been mentioned. 
In the cultivation of the mo it has especially been attempted 
to transform it into tin. By treating the soil and adding manure 
to it, it has been attempted to make the jadar plants grow here, 
and with some success. Hitherto, however, the object has been to 
transform a less southern to a more southern type of vegetation 
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