BULLETIN OF THE BUSSEY INSTITUTION. 67 
with a mixture of the two kinds of chemicals, as has usually been my 
custom. ‘The chemicals were here added on alternate days, as was 
stated on page 61. 
Cotton cloth was employed in these experiments in order that a 
loose, bulky material that contains no nitrogen might be put in con- 
trast with the bulky nitrogenous matters, such as the leathers and 
sponge. In case, moreover, any nitrogen from the air had been fixed 
in the soil, in a manner useful for plants, during the decay of the cot- 
ton,—as some chemists formerly thought might be the case, — the 
crops would have indicated such fixation. 
It is to be observed that the product obtained by roasting sheepskin 
was different from that obtained on roasting sole leather. It was not 
subjected to so high a temperature, and did not behave like the sole 
leather at any temperature. The appearance of the roasted sheepskin 
was unlike that of the roasted sole leather, and the two products 
differed from one another not a little in respect to their power of ab- 
sorbing water. The roasted sheepskin repelled water, so that it was 
difficult to moisten the mixtures of it and sand in the first place, and 
to keep them properly moistened afterwards, especially at the earlier 
stages of the experiments when the seeds were germinating. Hence 
the plants in this set of jars were rather less favorably placed than 
those in either of the other sets: they had to contend with unfavorable 
conditions, which, though not very important perhaps, may still have 
had an appreciable influence on the growth of the crops. Certain 
empyreumatic matters in the roasted sheepskin may, moreover, have 
possibly injured the plants a little directly, as any poisonous matter 
would ; and, on the other hand, it is not unlikely that tanning materials, 
or other matters, dissolved from the simple leathers, may have done 
some of the plants a suspicion of harm. It is true, at all events, that 
the seeds germinated with difficulty in the mixtures of sole leather 
and sand. 
One striking piece of evidence, in proof of the presence of some 
form of assimilable nitrogen in the roasted leather, was observed, as 
follows: After the series of thirty jars which contained the mixture 
of calcined loam and sand, and the various leathers, had been charged 
and put in position in the glass-house, and watered with nothing but 
rain-water for a fortnight, in order that the buckwheat seeds should 
germinate, an abundant growth of a salmon-colored fungus, which my 
