66 BULLETIN OF THE BUSSEY INSTITUTION. 
The crops obtained from the unroasted leathers weighed: 
SHEEPSKIN. SoLE LEATHER. 
0 (Sulph. potash) 0.130 —— 0.115 
1 (Phosp. potash) 0.055 0.120 0.100 0.120 0.150 0.110 
2 (Rain-water) 0.100 0.170 0.080 0.110 0.180 0.120 
That is to say, they were rather worse than the crops grown in mere 
sand. Corroborative evidence that the roasted products can supply 
some nitrogen to plants is to be found in the results obtained in jars 
Nos. 3 and 4, to which nitrogenous foods were purposely added, and 
in those from the jars numbered 5, which received a well-nigh com- 
plete mixture of foods. By comparing one with another the weights 
of the crops obtained in these jars, it will be seen that the results 
obtained with the roasted leathers are perfectly consistent with the 
conclusions just now announced. 
In all cases, the light, bulky materials, whether cotton, leather, or 
roasted leather, tended to interfere with the growth of the plants; 
evidently because the mechanical condition of the sands or loam with 
which these substances were mixed was inferior to that of the sands 
or loam to which no organic matter had been added. LBetter crops 
were obtained, for example, in jars Nos. 3, 4, and 5, that were charged 
with nothing but a mixture of sand and calcined loam, than in any of 
the other jars; but the roasted leathers did better, on the whole, in 
jars thus numbered, than the cotton or the simple leathers, both in the 
case of the calcined loam, and in that of the Provincetown sand. In 
the poor Berkshire sand, the influence of nitrogenous food is naturally 
very slight, no matter whether it be offered in the form of roasted 
leather, or in that of nitrate of potash or nitrate of lime, because in 
such sand the other kinds of plant food (potassic and phosphatic) are 
lacking. But even here, as well as in the other series of experiments, 
the marked leafiness and greenness of the crops in jars Nos. 3, 4, 5, 
and 6, went to show how much more efficient the nitrates were, as 
sources of nitrogen, than any of the materials that were supplied to 
jars Nos. 0, 1, and 2. It should be observed, in this connection, that 
the crops obtained from jars Nos. 5 and 6, in the Berkshire sand series 
of experiments, were smaller than I have usually obtained hitherto 
from such sand when supplied with the stated kinds of chemicals. 
The reason of this result appears to depend upon the fact that, in this 
particular series of experiments, these jars were not watered every day 
