260 BULLETIN OF THE BUSSEY INSTITUTION. 
contrasting the figures of the table on page 258 with those of the 
table next precedent, relating to green sand. It is highly improbable 
that either of the soils in the above list was richer in the inorganic con- 
stituents of plant food than green sand; and yet, thanks to the nitrogen 
natural to the peats and loams, they were able to bear, without any 
manuring, as good crops as were got from the green sand to which 
nitrates had been added. | 
The same point is still further illustrated by the experiments tabu- 
lated on page 259, which were made simultaneously with the experi- 
ments of page 258. The several jars contained similar mixtures of 
sand and loam, &c., in both series of experiments, but those of the table 
on page 259 were watered with a solution of phosphate of potash 
containing 0.25 gramme of that compound to the litre. 
Analogous results were obtained from another set of jars that were 
watered both with a solution of phosphate of potash and of sulphate 
of lime. Thus, for example, there was obtained from jar No. 3 in that 
case 2.530 grammes of dry crop, and, from jar No. 8, 0.19 gramme. 
The significance of the soil nitrogen will be seen from a somewhat 
different point of view in the following table of experiments (p. 261), 
made at the same time as the foregoing and under precisely similar con- 
ditions, in which the jars were watered with a liquid composed of equal 
volumes of a solution of nitrate of potash (1.25 grammes to the litre), 
and a solution of phosphate of potash (0.25 gramme to the litre). 
Many other experiments of this sort have been made with the sey- 
eral peats and loams, both by themselves and admixed with various pro- 
portions of sand; and these mixtures have been watered with solutions 
of different salts and mixtures of salts, but the results have always 
pointed directly to one and the same conclusion ; viz., that, the soil- 
nitrogen was readily made use of by the plants, except in those cases 
where the physical condition of the soil was unsuitable for their life and 
growth. 
It would be natural at this stage of the inquiry to illustrate the con- 
clusion still further by calcining the several soils in order to destroy 
their organic matter, and then growing plants in the residual sand or 
ashes; but there is happily no need of taking any trouble of that 
sort since E. Wolff has done the very thing already in certain experi- 
ments made by him long ago, to prove the utility of nitrates and of 
ammonium salts considered as manures. As the result of many trials, 
