REGENERATION MEASURES AND THE FORMATION OF SALTPETRE XCIII 
CHuaPr. IV. Clearings in mossy coniferous woods with nitrification 
appearing in the soil. 
(Detailed description on page 1032.) 
In a previous treatise (HESSELMAN, 1917) I have shown that in thé mossy coni- 
ferous woods the organic nitrogen of the soil is not transformed into saltpetre, 
but is absorbed by the plants either in the form of ammonia or in the form of 
more complicated organic compounds of nitrogen. This is also the case in 
the most productive mossy firwoods, as in the mixed woods, described in de- 
tail by SCHOTTE (1912), in the parish of. Björkvik in Södermanland, belonging 
to the communal forests of Jönåker Hundred. The wood in this part of the 
communal forest is cut by sections on the nurse-tree or shelterwood system 
(> Schirmhieb>). I have especially studied a series of clearings on an. Ose- 
gravel ridge (detailed description :on pp. ro31—1035). 
Before I proceed to a more detailed account of these clearings I wish to 
mention a few of the more important features of the stands that are cut. 
The stands consist of pine and spruce intermixed and belong to the usual 
type of mixed coniferous forest usual in central Sweden. The stands are very 
compact; bushes are lacking; undergrowth, such as red whortleberry, and bil- 
berry, occur both in small numbers and in most cases with small and weakly 
developed specimens. Grass and herbs play a very subordinate part. Here 
and there occur small patches of Majanthemum bifolium, sparse specimens of 
Luzula pilosa, and occasionally Trientalis europaea, Melampyrum silvaticum. 
Oxalis acetosella occurs only exceptionally; and sometimes one finds small 
patches of Anemone nemorosa. In the stands that are adjacent to the com- 
plete clearings studied the only grass is Luzula pilosa, while herbs are al- 
together lacking, with the possible exception of species of Melampyrum and 
Goodyera repens. "The ground covering is mainly composed of an even growth 
of moss, formed for the most part of IIylocomium parietinum and proliferum, 
which are our two commonest forest mosses, and of which the former forms 
the main part of the mossy covering. It lies quite loose on the ground and 
can easily be lifted up from the underlying humus covering. This humus 
covering has a looser structure, is partly mixed with mineral earth, but, ne- 
vertheless, belongs in the main to that type of humus which forms a crust on 
the ground. Isolated small worms are encountered. The form of humus which 
is found here differs from more marked raw humus in its greater looseness 
and smaller degree of toughness, and from separate mould in the fact that 
it forms a special covering to the underlying mineral earth. This form of hu- 
mus would seem to correspond pretty closely to what the Germans call '"Mo- 
der föPhechumus Mastacmarkedly? sour reaction; there" are no mtrl 
filcation) bacteria, amndnon,stonns, there are only a few traces of 
saltpetre. Under this covering of humus we come to a distinct, but not 
otherwise remarkable, crown of bleached soil, about three to four cm. thick, 
which rests on a' very loose layer of rust-red soil (see too, fig. 4). Both 
the profile of the ground and the covering of the ground are very charac- 
teristic of the better coniferous soils of central Sweden. 
When these stands are cut down, there occurs a very extensive change in 
the soil and in the vegetation. On one clearing, which was made in the 
winter of 1915—16, a sample of soil was taken at the close of May 1916 
