Scientific Intelligence — Botany. 371 



azote from the soil, the crops produced every year in manured 

 land giving a greater proportion of azote than is contained in the 

 soil itself. The question which he has proposed to himself for so- 

 lution is, whence then comes the excess of azote which the crops 

 contain, and in a more general manner, the azote of plants, which 

 the soil has not furnished % He divides his inquiry into the three 

 following parts : — 



First, Inquiry into and determination of the proportion of the 

 ammonia contained in the air of the atmosphere. 



Second, Is the azote of the air absorbed by plants ? 



Third, Influence on vegetation of ammonia added to the air. 



1st, The author remarks that, since the observation of M. Theo- 

 dore de Saussure, that the air is mixed with ammoniacal vapours, 

 three attempts have been made to determine the proportion of am- 

 monia in the air : a million of kilogrammes of the air, according to 

 M. Grayer, contain 0-333 kil. A2H 3 ; according to Mr Kemp 3 880 

 kil. ; according to M. Fresenius, of the air of the day, 0-098 kil., 

 and of night air, 0-169 kil. He states that he has shewn the 

 cause of these discrepancies, and proved that the quantity of am- 

 monia contained in the air is 22*417 grms. for a million of kilo- 

 grammes of the air ; and that the quantity oscillates between 17*14 

 grms. and 29*43 grms. 



2d, The author states that though the azote of the air is absorbed 

 by plants, the ammonia of the air contributes nothing to this ab- 

 sorption. Not that ammonia is not an auxiliary of vegetation, 

 but the air contains scarcely 0' 0000000224, and in this propor- 

 tion 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 anything from the soil. 

 For the present he confines himself to laying down these two con- 

 clusions : — 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 ap- 

 paratus 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 conducted, he ad- 

 duces the results of these experiments in proof of the above con- 

 clusions. 



3c?, 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 shews 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 



