XCIV HENRIK HESSELMAN. 
(31/5/16). The soil was then practically unaltered, and the moss-covering 
was still in good preservation except where it was strewn with withered nee- 
dles. No clearing plants had yet put in their appearance. The sample of 
soil taken from the clearing formed on storing only very small 
quantities of saltpetre (see Table 11, No. 1). But in the autumn of the 
same year a change had already become visible. When the clearing was visited 
on 7/,, 1916, there were found scattered specimens of Epilobium angustifolium, 
Rubus idaeus, Senecio silvaticus and Taraxacum officinale, that is to say several 
markedly saltpetre plants. 
Of these, Epilobium and Raspberry, as late as 7 October, gave a powerful 
nitrate reaction, but not Zaraxacum and Senecio. A total change in the 
conversion of the nitrogen has evidently begun to make its appear- 
ance. Saltpetre, which is mot formed in the ground whilestie 
trees remain, commences very soon, even during the first year, to 
be formed on the clearing to such an extent that nitratophilous 
plants can make their appearance and gather saltpetre into their 
tissues. The development now continues for some time in this direction, a 
fact which is further illustrated by the conditior.s on older clearings. 
A clearing from the winter of 1914—15 was examined at the same time 
as the above-named clearing at the end of May 1916. It had thus lain over 
a whole summer and was now entering upon its second year. The vegeta- 
tion of the clearing consisted of Epilobium angustifolium and Galeopsis bifida and 
a number of other herbs and grasses. On examination it appeared that £pzlo- 
bium, Galeopsis and Solidago virgaurea had gathered considerable quantities of 
saltpetre in their tissues, and that they gave a very powerful reaction with 
diphenylamine and concentrated sulphuric acid. A sample of soil from this 
clearing, taken on 31 May 1916, at the same time as the samples from the 
stand and the clearing of the winter of 1915—16, formed, on being stored, 
considerable quantities of saltpetre (see too Table 11, No. 2). Thus when 
the clearing Has lain a summer, the formation of saltpetre sken. 
tremely active. 
The same is also the case with a clearing from the winter of 1914. To judge 
from the samples stored, the formation of saltpetre is still more active 
than in the clearing which is a year younger (see too Table rr NOS: 
On the oldest clearing in this same series, situated on the same ground 
and with the same exposure, the vegetation of the clearing is very rich. The 
clearing was made in the winter of 1911—12, and had thus, at the time of 
investigation (29—31 May, 1916), lain four summers. Amongst the plants 
of the clearing may be noticed, in addition to Galeopsis bifida, several of 
our most common tilth-weeds, such as sow-thistle (Sonchus arvensis), common 
field thistle (Cirszum arvense) and spear-thistle (Cirstum lanceolatum), and several 
others. In the old burnt patches, where the spruce brushwood had been 
burnt up, may be noticed also nettles (Urtica dioica). Epilobium, which had 
now probably grown for four years on the clearing—ever since the summer 
of 1912—n0 longer gives any nitrate reaction, whereas raspberry, Sonchus ar- 
vensis and Cirsium lanceolatum do (detailed descriptions page 1034). The 
samples of soil from the clearing show on storing considerable quantities of 
saltpettes($ee too tablel 11, NO: 4). 
A still older clearing lies quite close to the stand described above, but 
