70 BULLETIN OF THE BUSSEY INSTITUTION. 
On the 29th March, one of the plants in jar No. 3 was taken up, dead. 
Yet, at the time of harvest, the crops from the calcined loams weighed 
only from 0.15 to 0.195 grm.; while the crop from the mixture of green 
sand and roasted leather weighed 0.78 grm., in spite of the premature 
death of the plant just mentioned. 
As regards the roasted sheepskin, in jar No. 2, it was plain from 
the appearance of the plants that this material actually did harm in the 
earlier stages of growth. One of the plants in this jar died before 
the end of March, and another somewhat later. But the plant finally 
harvested, though very small, was green in all its parts, and had evi- 
dently procured a little nitrogen, in some form, from the roasted 
sheepskin. 
At the time when this series of experiments was made, it was 
thought that the peculiarly wretched appearance of the crops might 
be due in some part to the compact character of the green sand: it 
lay dense and heavy in the jars, and its closeness of texture seemed 
to have some connection with the manifest distress of the plants. But 
the results obtained since that time with the mixture of calcined loam 
and sand, as given above, in which the well-fed plants prospered, and 
the ill-fed did not prosper, as well as the large weight of the crop that 
was obtained from the green sand by means of nitrate of lime (jar 9), 
go to show that the small crops from the green sand were really due 
not so much to bad mechanical condition of the soil as to an actual 
want of nitrogenous food. 
The general conclusion to be drawn from all these experiments 
seems to be, that while ordinary leather is absolutely worthless as a 
fertilizer, roasted leather has a certain small value, depending upon the 
presence in it of some form of assimilable nitrogen. It would be of 
interest to determine, by analysis, what the substance or substances 
really are in the roasted leather which are useful to plants, to ascertain 
how much of them are present at the best, and to determine what tem- 
peratures are most favorable for their formation. But there is nothing 
in the present investigation, nor is there elsewhere any evidence that I 
know of, to invalidate the common impression that nitrogenous plant- 
food can probably be obtained both in larger quantity, and at a cheaper 
rate, by distilling leather with soda-lime or potash-lime, than by any 
method of mere roasting, without addition of chemicals. 
There is but little, moreover, in the results above given, to encourage 
