EXPERIMENTS ON VEGETATION IN SOLUTIONS. 357 



remarkable change was however produced. Scarcely five hours 

 elapsed before the growth of the plant, which had been stationary 

 for four weeks, awakened to a new life, and proceeded from this 

 time forth in the best manner possible. A plant without the after 

 addition of nitrate of lime remained stationary, making no progress 

 whatever : the maize plant, therefore, requires lime immediately 

 after the commencement of its growth. 



In an experiment in which the magnesia was replaced by nitrate 

 of lime, the same result was obtained as when lime was wanting. 

 In this case, also, the vegetation was very poor. A supply of mag- 

 nesia in the form of nitrate, exerted here also the most favourable 

 action, only the effect was not so quickly produced as in the case 

 of lime. 



Even by the complete withdrawal of nitric acid the maize 

 plant did not grow. In these experiments it is true the alkalies, 

 as well as the alkaline earths, were in part supplied in the form of 

 sulphates and chlorides. Chlorine and sulphuric acid, however, 

 are required only to a limited extent in the vegetable organism. 

 The same holds good in the experiment without nitrogen. Ac- 

 cording to these experiments, therefore, a plant is not developed 

 if one of its elements of food is wanting, and the complete re- 

 placement of one element of food by another one similar to it, is 

 hence completely out of the question, The result may, however, 

 be different with the reciprocal partial replacement of similar ele- 

 ments of food ; and Stohmann is about to take up this question. 



The form in which the food was supplied was the following.* 

 The silicic acid was always supplied in the form of silicate of pot- 

 ash ; the potash as nitrate. In the series of experiments (3) which 

 were made without nitric acid, sulphate of potash was used in- 

 stead of the nitrate. 



The phosphoric acid was used in the form of 2UaO, HO, P0s + 

 24HO ; in experimental series 5, in which soda was excluded, a 

 potash salt was used, 2KO, HO, PO 5 , of which a concentrated so- 

 lution was prepared, containing a known quantity of potash and 

 phosphoric acid. As the phosphate of soda contained more soda 

 than was requisite in the composition of the ash, there was thus in 

 the fluids in the experimental series 1 to 7 an excess of this base ; 

 at a later period, a correspondingly smaller quantity of phosphate 

 of soda and more of the potash salts were employed. 



The sulphuric acid was in the form of sulphate of magnesia, 

 with the exception of 7, in which sulphate of ammonia was used, 

 the magnesia required was added in the form of, nitrate of mag- 

 nesia. 



The oxide of iron was supplied in the form of pure sublimed- 



* To form a complete solution of all matters, and to remove the alkaline 

 reaction, the fluid was first properly diluted with water and so much weak 

 hydrochloric and later phosphoric acid was added as to make the reaction 

 distinctly feebly acid. 



