REGENERATION MEASURES AND THE FORMATION OF SALTPETRE CI 
the greatest interest. There is a more detailed account on page 1044. As 
appears from fig. 15 the experiment took place on a clearing with a dense 
crop of seed-trees of pine. Where the machine used for preparing the soil 
disturbed the ground very much, raspberry and £pilobium appear in the cover- 
ing of the ground, and younger plants gave nitrate reaction as late as October. 
Where, on the other hand, the Finnish plough did not disturb the ground, 
the ground-covering was practically unaltered and had practically the same 
character as in the adjacent dense wood, that is to say the ground covering 
consisted of the usual forest mosses and berry shrubs. As I have never de- 
tected nitrification in any ground with such covering, I have every reason to 
suppose that it was lacking in this case also. The preparation of the soil 
watch ther rimnishe plomah has thus produced in this case al nen 
Gatron that does mot occ im] m thevcundisturbed ground: 
What has been here adduced shows that the preparation of the ground 
carried out in such a way that the humus covering is at any rate in part 
mingled with the mineral soil is calculated to produce nitrification, even when 
that process is lacking in the undisturbed soil. 
CHaAP. VII. The effect of burning on the transformation of 
nitrogen in the soil. 
(Detailed description on page 1046.) 
In connection with complete felling, with or without preparation of the soil, 
burning or denshiring has attracted the greatest attention when the question 
was raised of regenerating our forests. Fire has indeed played an extremely 
important part in the development of our natural forests, especially in Norr- 
land. There it would be very difficult to lay out a single square metre of 
a large sample-plot in the forest land of such a nature that under the 
upper layer of humus there could not be shown the existence of charcoal 
composed of remains from some forest fire, which in older or more recent 
times had passed over the place. Under such circumstances it would seem 
to be justifiable to give a somewhat detailed account of the effect of fire on 
the ground, and especially on its transformation of nitrogen. 
There is a general agreement that fire has promoted the regeneration of 
coniferous forests. Hitherto the cause of the effect of fire would seem to 
have been usually sought in the ashes that are produced, and which would 
seem to manure the young tree plants. But as we can very often trace for 
a long time a favourable effect of the burning on the ground, this can 
scarcely be the sole cause, as the easily soluble ashes are soon washed out. 
As an example of this it may be mentioned that one year after the burning 
it is impossible with hydrocloric acid to show the existence of any carbonates 
in the ground, just as little as in a charcoal-burning ground which has been 
used in the preceding winter. The main importance of the burning 
really lies in the influence which it exercises on the transforma- 
tion of nitrogen on the soil. 
In Norrland there are chiefly two plants that characterize burns or den- 
shired ground, namely fireweeds (Epilobium angustifolium) and raspberry or 
