136 
quent and violent, there is a very large amount of nitric acid, either 
free or combined, in the rain water. The relative values in different 
climates are as follows: 
Weight of 
nitrogen 
per meter 
rainfall 
per hec- 
. tare. 
Locality. 
Kilos. 
A baveyarel wave hore 1gdeypbabloyn. se ee oS lwo AN NES ORs DUS Se es ee ee 6.93 
Waracast ass 12a. See has eae ee aie eee pL S28. ee es Soe ee eee eee 5.78 
Rothamsbedtes.20 20.8. es ee ee ee ee eee eee ee 0. 88 
Wuiebfrauenbere ~ (228. 6 22a fo gaa eaen ae ee Se ee see aa ee See 0, 33 
NITROGEN DIRECTLY ABSORBED BY THE SOIL. 
Schloesing has shown that the atmospheric ammonia has its in- 
fluence upon the plant greatly multiplied by the direct absorption 
of this ammonia from the air into the soil. The absorption is greatest 
when the difference between the tension of the ammonia in the soil 
and that in the atmosphere is at a maximum; it is therefore greatest 
when the soil is moist and when nitrification converts the ammonia 
into nitrates as fast as it is absorbed. When the earth is dry nitrifi- 
cation is suspended, and the ammonia accumulates in the soil up to 
a certain point, beyond which the rate of absorption gradually 
diminishes. (Agr. Sci., Vol. IV, p. 292.) 
FIXATION OF NITROGEN BY PLANTS. 
Experiments as to the source whence the grains (Graminee) and 
the beans and peas (Leguminose) derive their nitrogen have been 
made both in Germany and France by independent methods. Thus 
Hellriegel and Wilfarth from 1883 to 1887 experimented upon sam- 
ples of these plants, each of which was placed in a pot of sterilized 
quartz sand to which was added a nutrient solution, and the plants 
were watered with distilled water so as to keep the conditions favor- 
able to growth. The results were that oats and barley behaved alike ; 
when they are not furnished with nitrates there is no development 
beyond the reserve in the seed, and when they are fed with nitrates 
the harvest of dry matter is directly proportioned to the quantity of 
nitrate. For every milligram of nitrogen the increase of dry matter 
is 93 milligrams for barley and 96 for oats, respectively. Steriliza- 
tion of the soil and of the pots on the one hand, and the addition of 
the microbes contained in the washings of cultivated soil on the other 
hand, cause no variation in the above results. 
Peas behave quite differently from the preceding. Some plants 
languish if they have no nitrates, but others suddenly acquire new 
