Royal Society. 145 



tained in the air is 22*417 grms. for a million of kilogrammes of the 

 air; and that the quantity oscillates between 17*14 grms. and 

 29*43 grms. 



2. The author states that though the azote of the air is absorbed by- 

 plants, the ammonia of the air contributes nothing to this absorption. 

 Not that ammonia is not an auxiliary of vegetation, but the air con- 

 tains scarcely 0*0000000224, and in this proportion its effects are 

 inappreciable. These conclusions are founded upon a great number 

 of experiments in which the plants lived at the expense of the air 

 without deriving any thing from the soil. For the present he con- 

 fines himself to laying down these two conclusions : — 1 . The azote 

 of the air is absorbed by plants, by the cereals, as by all others. 2. 

 The ammonia of the atmosphere performs no appreciable part in the 

 life of plants, when vegetation takes place in a limited atmosphere. 

 After describing the apparatus by means of which he carried on his 

 experiments on the vegetation of plants placed in a soil deprived of 

 organic matter, and the manner in which the experiments were con- 

 ducted, he adduces the results of these experiments in proof of the 

 above conclusions. 



3. With reference to the influence of ammonia on vegetation, the 

 author states that, if ammonia be added to the air, vegetation be- 

 comes remarkably active. In the proportion of 4 ten-thousandths 

 the influence of this gas shows itself at the end of eight or ten days, 

 and from this time it manifests itself with a continually increasing 

 intensity. The leaves, which at first were of a pale-green, assume 

 a deeper and deeper tint., and for a time become almost black ; their 

 petals are long and upright, and their surface wide and shining. In 

 short, when vegetation has arrived at its proper period the crop is 

 found far beyond that of the same plants grown in pure air ; and, 

 weight for weight, they contain twice as much azote. Besides these 

 general effects there are others which are more variable, which de- 

 pend upon particular conditions, but which are equally worthy of 

 interest. In fact, by means of ammonia we can not only stimulate 

 vegetation, but, further, we can modify its course, delay the action 

 of certain functions, or enlarge the development and the modifica- 

 tion of certain organs. The author further remarks, that if its use 

 be ill-directed, it may cause accidents. Those which have occurred 

 in the course of his experiments appear to him to throw an unex- 

 pected light upon the mechanism of the nutrition of plants. They 

 have at least taught him at the expense of what care ammonia may 

 become an auxiliary of vegetation. These experiments, which were 

 made under the same conditions as those upon the absorption of 

 azote, are then described, and their numerical results given. 



To the conclusions already stated, the author adds that there are 

 periods to be selected for the employment of ammonia, during which 

 this gas produces different effects. If we commence its use when 

 several months intervene before the flowering season of the plants, 

 it produces no disturbance ; they follow the ordinary course of their 

 vegetation. If its use be commenced at the time of flowering, this 

 function is stopped or delayed. The plant covers itself with leaves, 

 and if the flowering takes place all the flowers are barren. 



Phil. Mag. S. 4. Vol. 6. No. 37. Aug. 1853. L 



