DR. J. II. QTLBERT ON CLOYER-SICKNESS. 
93 
tain a large proportion of carbonate, indicating, possibly, that 
the fixed bases had been taken up in combination with a com- 
bustible organic acid. Again, another fact in accordance with 
the view is, that although a Leguminous crop assimilates two, 
three, or more times as much nitrogen over a given area as a 
Graminaceous one, the direct application of ammonia- salts, so 
eifective with the latter, is more frequently injurious than bene- 
ficial to the former within the season of their employment ; 
though, after some time has elapsed, some beneficial effects can 
be observed, apparently due to the previous supplies. An obvi- 
ously possible explanation of this is, that organic acid salts of 
ammonia have have been formed. 
On the other hand, nitrate of soda, though not a reliable ma- 
nure for Leguminous crops, as it and ammonia-salts are for tlie 
Grraminacese, is certainly much more beneficial to them than are 
ammonia-salts ; and, it may be, that it is not until the ammonia 
has in great part been converted into nitric acid, and the result- 
ing nitrates become widely distributed throughout the pores of 
the soil and subsoil, that the Leguminous plant attains suffi- 
ciently active and vigorous growth, and acquires sufficient posses- 
sion of the soil, to render it independent of its many enemies — 
whether in the form of animal or vegetable parasites, or of cli- 
matic vicissitudes which slacken its vitality, and render it an 
easier prey to its animal or vegetable enemies. 
On the supposition that the favourable condition of the ni- 
trogen is that of ammonia in combination with an organic acid, 
we have to conclude that that condition, even if favourable, is at 
any rate not essential for the Grraminaceous crop, or that the 
distribution of the compounds in question is such as to render 
them not so readily available for the Graminaceous as for the 
Leguminous plants. Supposing, however, that the required con- 
dition be the oxidation of the ammonia and the wider distribu- 
tion of the nitrogen in the form of nitrates than would take 
place so long as it remained as ammonia, that portion of the 
nitrogen which is supplied in manure for the Graminaceae, and 
which, owing either to unfavourable combination, or unfavour- 
able distribution, within the soil, is not recovered in the increase 
of the immediate crop, becomes gradually oxidated and more 
widely distributed, and the Leguminous crop, alternating with 
the Graminaceous one, and gathering from a more extended or 
different range of soil, in its turn leaves a residue, or allows the 
