CXNXII HENRIK HESSELMAN. 
tree-plants developed in such places show, too, by their stronger, darker nee- 
dles, and by their stronger growth, that they are able to absorb the saltpetre 
nitrogen. 
The measures which ought to be taken depend both on the nature of the 
ground and on the nature of the clearing. In many of the more or less 
extremely sparse spruce-forests of Norrland one finds under the trees quite 
numerous spruce-plants which have managed to germinate in the half-shade 
of the spruce-forest and have there led a languishing life. When the forest 
is felled and the light is admitted, these trees begin to grow apace; and if 
they are sufficiently close together, they may sooner or later form a stand 
(see fig. 42). The development of these spruce plants, however, is connected 
with the transformation of the humus-covering: a more active conversion 
must take place. In a clearing where there are plenty of such plants and 
where the humus covering is rapidly transformed, there, too, we have every 
reason to take what nature offers and let these spruces enter into or form the 
new stand (see fig. 43). The difficulties lie principally in getting such a stand 
sufficiently dense: to fill up any gaps that exist by auxiliary planting, how- 
ever, is a thing which ought to be attempted. Whether this is successful or 
not depends mainly on the nature of the ground and, above all, on the trans- 
formation of the nitrogen. The prospects of this are greatest when the humus 
nitrogen is nitrified, for there it is possible to raise pines even in relatively 
small open spaces (see fig. 44). 
Of late there has been a tendency to adopt clean cutting without burn- 
beating or burning and planting of one or two years old pine-plants that have 
not been raised in a nursery. These plantations have given very various re- 
sults; but even where they have succeeded, of course, there is some doubt as 
to whether the method can be regarded as quite satisfactory. On clearings 
with Azra flexuosa the planted plants are not so strong as where nitrification of 
the humus nitrogen has been produced; and self-sowing is not much to be 
relied upon, as the blanket of Azra flexuosa 1s an unsuitable germinating bed 
for coniferous tree-seed. If one relies solely on culture, the stand will be 
very sparse: and in the diseases to which the pine in particular is exposed 
we have far too small a number of plants in reserve to fall back on. I 
scarcely believe, therefore; that in the long run this method will prove to 
satisfy the claims which may fairly be made on regeneration. It will be costly 
in proportion to its efficacy, and it leaves far too little room for natural re- 
growth. The treatment of the clearings should, as far as possible, aim at 
producing such alterations in the humus-covering as strongly nourish the 
sown or planted plants and, at the same time, promote natural regrowth. 
In the brushwood left on the ground we have not infrequently the means 
of producing the nitrification of the nitrogen. In the forests under Garpen- 
berg we find that Azra flexuosa is often the dominant plant on the clearing, 
but that nitratophilous plants are found in the piles of brushwood. The 
brushwood there is often piled in such high heaps, however, that all na- 
tural regrowth is rendered impossible; but where the brushwood is not too 
abundant, its even and uniform spreading over the clearing may often promote 
not only the development of the sown or planted plants but also the na- 
tural regrowth. In the Black Forest in Germany branches of the silver fir 
(Abies alba) are employed in the same way in order to promote the transformation of 
