161 
floating in the air and were deposited in the pots in which the plants 
grew. As a rule, the greater the abundance of tubercles the more 
vigorous were the plants and the greater the gain in nitrogen. The 
gain of nitrogen from the air by the legumes explains why they act as 
renovating crops. (Agr. Sci., Vol. IV, p. 22.) 
~ From some careful experiments by A. Petermann on yellow lupins 
(Lupinus luteus) the author concludes that the physiological réle of 
the tubercles must not be exaggerated. They can not be the only 
cause of the fixation of nitrogen, although their presence may explain 
why the intervention of atmospheric nitrogen is most marked in the 
‘ase of the Leguminose. He further shows that sodium nitrate is not 
injurious, but beneficial, to lupins. The trouble in its use results 
mostly from the fact that it is very soluble and is soon washed down 
by the rain out of the reach of the roots, which must then draw their 
nitrogen from the atmosphere by means of the microbic organisms. 
(Agr. Sci., Vol. IV, p. 264.) 
Pagnoul has measured the loss and gain of nitrogen by the soil as 
the result of the cultivation of special crops. He sowed grass and 
clover in four pots, but left two others without any crop. The gain 
of nitrogen permanently fixed in the soil in one year—March, 1888, to 
March, 1889—was as follows: With no crop the soil gained at the 
rate of 29 kilograms per hectare per year, with the grass crop 394 
kilograms, and with the clover crop 904 kilograms. On the other 
hand, the total proportion of nitrogen removed from the soil by the 
drainage water was in each case as follows: No crop, 85; grass, 5; 
clover, 18. (Agr. Sci., Vol. IV, p. 325.) 
11 
2667—05 M 
