NUTRIENT GASES. 65 
Ammonia behaves in relation to plants just in the same way as carbon-dioxide 
and nitric acid. It is disengaged from dead decomposing organic bodies, and is 
found in traces, either alone or with equally minute quantities of earbon-dioxide 
and carbonic and nitric acids in the air, in atmospheric deposits, and in all water 
wherein animals and plants reproduce their kind, the old individuals dying and 
making way for the young. Water-plants are all limited to this source for acquisi- 
tion of nitrogen. As regard lithophytes, it stands to reason that they must derive 
their nitrogen from the ammonia contained in the air, in atmospheric deposits, 
and from nitric acid. Whence otherwise could a crustaceous lichen attached to a 
quartz rock on a mountain supply itself with the nitrogen essential for the growth 
‘of its protoplasm? Moreover, some of the larger lithophytes, especially mosses, 
seem to be capable of absorbing ammonia direct from the air. An observation 
made in the Tyrolese Alps has some bearing on this question:—The ridges of the 
Hammerspitze, a peak rising to 2600 meters between the Stubaithal and the 
Gschnitzthal, is, in favourable weather in the summer, the resting-place of hun- 
dreds of sheep, and is consequently covered with an entire crust of the excrements 
of these animals. A highly offensive and pungent smell of ammonia is evolved, and 
renders a prolonged stay on this spot anything but pleasant, notwithstanding the 
beauty of the view. Now, it is worthy of note that the mosses, which are produced 
in abundance on the rocks above this richly-manured ground, but are not them- 
selves actually amongst the sheep-droppings, exhibit a luxuriance unparalleled on 
any of the neighbouring summits belonging to the same formation but unfre- 
quented by sheep. The gaily-coloured green carpet extends as far as the ammo- 
niacal odour is perceptible, and it is natural to suppose that this luxuriant growth 
is stimulated by the absorption of ammonia direct from the air. 
Land-plants also can take up ammonia from the air. It has been shown that 
the glandular hairs of many plants, for instance those on the leaves of Pelargoniwm 
and of the Chinese Primrose, have the power of absorbing traces of ammonia, and 
of sucking up carbonate and nitrate of ammonia in water with rapidity. When we 
consider that a single one of these primroses (Primula sinensis) possesses two and 
a half millions of absorbent glandular hairs so placed as to be able to take up the 
ammonia brought to the plant by rain, we are unable to look upon this process as 
of altogether trifling importance. It is highly probable that almost all ammonia, 
after its formation from decaying substances in the ground, is at once absorbed by 
the plants growing in the immediate neighbourhood, and that the relatively small 
quantity of ammonia in the upper atmospheric strata is referrible to this cause. 
The splendid luxuriance of the pelargoniums, thickly studded with glandular hairs, 
which one sees in front of cottage windows in mountain villages where a dung 
heap is close by, and in the windows of stables, frequently excites admiration and 
surprise. Whether it is due to the fact that in these situations there is the possi- 
bility of absorbing an unusually large quantity of ammonia is a question which we 
will leave undecided. 
Vou. I. 5 
