REGENERATION MEASURES AND THE FORMATION OF SALTPETRE KEY 
the ground consists of moraine, not of ose-gravel. The clearing dates from 
the winter of 1910—11 and was put into order in the spring of 1912. It 
was examined' both in the spring of 1915 and in the spring of 1916, that 
is when the clearing was four and five years old respectively (A further de- 
scription is given on page 1034). In the spring of 1916 there was observed 
powerful nitrate reaction in the raspberry, nettles, and some specimens of 
Epilobium angustifolium and Galeopsis bifida. Samples of soil taken in the 
spring of 1915 formed on being stored considerable quantities of saltpetre 
(see Table 11, No. 5). From this clearing there were also taken samples of 
soil for bacteriological investigation. These samples show a great capacity 
for producing ammonia (see Table 1, No. 12), nitrify very slowly a solution 
of sulphate of ammonia, and denitrify GILTAY's solution rapidly and with an 
detkyektormation. oftgaskseentoor Tab. dö; No. 6); In these respectsithe 
bacterial flora agree with that of the pure mould. 
The clearings here described show how the cutting itself, and the 
greater supply oflight that cutting brings with it, can, under favour- 
able conditions, bring about a radical change in the modes of trans- 
formation of the nitrogenous composition of the ground. Saltpetre- 
forming bacteria, which are lacking, or which cannot be demon- 
strated, in the ground so long as the stand is dense, immigrate 
quickly and are already to be found on the clearing in the autumn 
of the first year. A very active nitrification begins, which favours 
the appearance of markedly nitratophilous plants, including a 
number of tilth-weeds. At the same time, however, the humus covering 
itself undergoes a number of alterations. The structure becomes more and 
more mould-like, and the tendency to flocculated structure, already visible 
when the ground was covered with trees, becomes more and more marked 
on the cleared ground. But the humus covering still retains its capacity to 
give an acid reaction. 
The stands now described at Jönåker exhibit the same radical changes in 
modes of transformation in nitrogenous composition when small gaps are exam- 
ined (see too, fig. 5). In these both raspberry and Kpilobium angustifolium 
are wont to appear, and the formation of saltpetre is very active. In a gap 
about fourteen years old, removed because the spruces had been killed by 
attacks of bark-borers, Trientalis europaea, Luzula pilosa and raspberry gave a 
very strong nitrate reaction. On the other hand, negative results were obtained 
with Majanthenum bifolium and Epilobium angustifolium (older and fully deve- 
loped specimens). Within the dense wood numerous specimens of Luzula pilosa 
were collected, all of which gave negative results on being tested for nitrate. 
The mixed coniferous forests in central Sweden often present the same 
phenomenon as the woods in the communal forests of Jönåker Hundred. As 
example may be mentioned the forests under Alkvettern in Värmland. No 
analyses of the humus covering in these woods have been made, but the struc- 
ture, the nature of the ground, and the covering of the ground, etc. show 
that the humus-form occurring there is so near akin and so similar to that 
which occurs in the Jönåker woods that I am sure that no nitrification oc- 
curs. Nor have I been able to demonstrate any nitric acid in the herbs that 
cover the ground of the wood, for instance, Luzula pilosa. The vegetation 
which is found in gaps and on larger clearings, on the other hand, is a 
