No. I.
_Effects of Nitrous Oxide on Vegetation._
In July 1799, I introduced two small plants of spurge into nitrous
oxide, in contact with a little water over mercury; after remaining
in it two days, they preserved their healthy appearance, and I could
not perceive that any gas had been absorbed. I was prevented by an
accident, from keeping them longer in the gas.
A small plant of mint introduced into nitrous oxide and exposed to
light, in three days became dark olive and spotted with brown; and in
about six days was quite dead.—Another similar plant, kept in the dark
in nitrous oxide, did not alter in color for five days, and at the end
of seven days, was only a little yellower than before. I could not
ascertain whether any gas had been absorbed.
I introduced into nitrous oxide through water, a healthy budding rose,
thinking that its colors might be rendered brighter by the gas. I was
disappointed, it very speedily faded and died; possibly injured by the
solution of nitrous oxide in water.
Of two rows of peas just appearing above ground; I watered one with
solution of nitrous oxide in water, and the other with common water
daily, for a fortnight. At the end of this time, I could perceive no
difference in their growth, and afterwards they continued to grow
equally fast.
I introduced through water into six phials, one of which contained
hydrogene, one oxygene, one common air, one hydrocarbonate, one
carbonic acid, and one nitrous oxide, six similar plants of mint,
their roots being in contact with water and their leaves exposed to
light.
The plant in carbonic acid began to fade in less than two days, and
in four was dead. That in hydrogene died in less than five days; that
in nitrous oxide did not fade much for the first two days, but on
the third, drooped very much, and was dead at the same time as that
in hydrogene. The plant in oxygene for the first four days, looked
flourishing and was certainly of a finer green than before, gradually
however, its leaves became spotted with black and dropped off one by
one, till at the end of ten days they had all disappeared. At this
time the plant in common air looked sickly and yellow, whilst that in
hydrocarbonate was greener and more flourishing than ever.
I have detailed these experiments not on account of any important
conclusions that may be drawn from them; but with a view of inducing
others to repeat them, and to examine the changes effected in the
gases. If it should be found by future experiments, that hydrocarbonate
generally increased vegetation, it would throw some light upon the use
of manures, containing putrefying animal and vegetable substances, from
which this gas is perpetually evolved.
The chemistry of vegetation though immediately connected with
agriculture, the art on which we depend for subsistence, has been but
little investigated. The discoveries of Priestley and Ingenhousz, seem
to prove that it is within the reach of our instruments of experiment.
No. II.