REGENERATION MEASURES AND THE FORMATION OF SALTPETRE CRV 
pale-green needles indicate a weaker supply. An examination of the 
soil confirms this surmise. On being stored for seventeen weeks the following 
quantities of nitric acid were formed:— 
Humus Humus 
collected collected 
under trees. — between trees. 
PRIFOSen Was thitratenper Ke: OÅ.SOL oss osssasssgesn da 24 mg. 0.4 mg. 
Nitrogen as a percentage of the dry weight of 
ER on fr SR EE Se EA MEAN, 0.43 4 0:29 
Nitrogen in percentage of loss on ignition in the 
SOL (LÄRT IS a rr ma mans vbeeor as EAS K.O7 VG 203 
'The experiment tells strongly in favour of the idea that the nitrifica- 
tion of the humus nitrogen is of very great importance for the 
strong development of the pine-plants in their youth. I shall further 
illustrate this matter in the next article as regards the pine-heaths: here I 
wish to adduce some observations from other types of forest. If one com- 
pares the pine-plants standing in ground covered with Azra flexuosa, where the 
nitrogen is not nitrified, with such as grow, for instance, in places where the 
brushwood has been burnt, it is found that the latter are usually taller and 
stronger and have far darker and stronger needles than the former. One might 
possibly be tempted to believe that this was a direct result of manuring by 
the ash formed at the burning. But this is by no means the case. 
As I have pointed out above in this article, there are often in spruce-forest 
clearings certain parts where the nitrogen is nitrified, although in most places 
it is only converted into ammonia. Such places are found, as a rule, in the 
neighbourhood of stumps etc. In Svartberg Crown Park in Degerfors revir I 
examined, in the autumn of 1916, some clearings made in fairly old spruce 
forest or mixed coniferous spruce forest. On the unburnt clearings there were 
usually found only shrubs and Azra flexuosa. On the unburnt parts there 
were found here and there plants which were quite as strong as 
or even stronger than those which occur on the burnt parts ofthe 
clearing, and which had the same healthy dark-green apperance as 
the plants on the burnt parts. These plants occur exclusively in spots 
where one could also find scattered specimens of Rumex acetosella, Rubus idaecus, 
Epilobium angustifolium, and they were found on examination to contain nitrate. 
The strong dark-green plants on the unburnt parts thus grew in 
spots where the humus nitrogen was nitrified. Samples of earth on 
storage afterwards showed an active power of nitrification in the ground (see 
tablePis;mO=3): 
Direct Observations in nature, and. also experimental studies, 
show with all desirabie clearness that the types of humus that are 
formed in our mossy coniferous forests, or on our pine-heaths in 
Norrland, are most favourable to the young pine-plants when in 
some way or other they pass into a nitrifying saltpetre-forming 
stage. It is most probable that the explanation of this lies in the greater 
accessibility of the nitrogen, although it is also possible, of course, that other 
nutritive substances in the humus-covering become more easily accessible to 
