168 THE YEAR-BOOK OP AGRICULTURE. 



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 at- 

 mosphere. 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 conducted, 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 am- 

 monia be added to the air, vegetation becomes remarkably active. In the proportion of four 

 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 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 growing in pure air, and, weight for weight, they contain twice as much nitrogen. Be- 

 sides these general effects, there are others which are more variable, which depend upon par- 

 ticular 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 modification 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 unexpected 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 nitrogen, are then de- 

 scribed, 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 com- 

 mence its use when several months intervene before the flowering season of the "plants, it pro- 

 duces no disturbance ; they follow the ordinary course of 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. 



Chemical Investigation of the Phenomena of Vegetation. 



THE following are the details of experiments recently presented to the French Academy 

 by M. Boussingault, on the phenomena of vegetation, the researches described being mainly 

 undertaken for the purpose of settling the question, whether plants obtain their supplies of 

 nitrogen from the atmosphere directly, by absorption: 



On the 17th of May, 1854, the author sowed three seeds of the garden-cress (Cresson 

 aUnoisa) in a flower-pot containing three kilogrammes of earth ; and at the same time three 

 similar seeds were placed in the same quantity of earth, enclosed in a glass vessel capable of 

 containing 68 litres, which was then closed so as to exclude all air. On the 16th of June, 

 the plants in the closed space were twice as large as those in the flower-pot, which had 

 remained in the open air. On the 15th of August, the plants were collected : the enclosed 

 plants had flowered normally, and bore the usual quantity of ripe fruit. 



In the second series of experiments, the seeds were placed in a soil which had previously 

 been calcined. To this the ashes of various plants were added. The plants vegetated in an 

 air-tight case of plate glass, capable of containing about 104 litres. Air was then constantly 

 drawn in by an aspirator, after passing over pumice-stone moistened with sulphuric acid. 

 By a simple arrangement of the apparatus, carbonic acid was allowed to enter the receiver 

 in such quantity, that the air carried with it from 2 to 3 per cent, of this gas. The pumice- 

 stone in which the seeds were placed was contained in pots containing 4 decilitres ; the pots 

 being previously heated to redness. The ashes were prepared with particular care, in order 

 that no carbon should be mixed with them. The carbon, which is of no consequence in itself, 

 would possess an influence if nitrogenous bodies were contained in the ashes. The amount 



