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 carbon-dioxide 

 and cai-bonic 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 contamed 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 Pelargonium 

 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. 



