CHEMICAL SCIENCE. 263 



occupied myself in investigating still further the interesting subject, and I 

 have now to announce the addition of two substances to the list of those 

 capable of furnishing nitrogen to plants, namely, nitrate of potash and ferro- 

 cyanide of potassium. The experiments by which I succeeded in proving 

 the availability of these bodies, as food for plants, were conducted in the 

 following manner : 



A number of peas were selected, some of which were dried, submitted to 

 analysis, and found to contain 4.365 per centum of nitrogen. Others were 

 sown under the following circumstances : five earthenware vessels, respec- 

 tively labelled Nos. 1, 2, 3, 4, and 5, were partly filled with brick-dust, and in 

 each were sown eight peas. These were manured with a mixture composed 

 of the following ingi'edients : The double silicate of potash and soda, chloride 

 of sodium (common salt), carbonate of lime (chalk), hydrated sulphate of 

 lime (gypsum), freshly precipitated phosphates of lime and magnesia, and 

 calcined bones. In addition to this compound, which, it will be perceived, 

 was altogether destitute of nitrogen, Nos. 1 and 2 were supplied with ferro- 

 cyanide of potassium, and Nos. 3 and 4 with nitrate of potash. Both of 

 these substances are well known as nitrogenous compounds. No. 5 was left 

 without any nitrogenous substance. The vessels were placed under glass 

 shades, and supplied with sufficient light, and with air freed from the slightest 

 trace of ammonia or of nitric acid. 



The seeds were sown on the 28th of March, I860, and, with three excep- 

 tions, germinated and developed into plants. Daily, during the growth of 

 plants, they were supplied with carbonic acid, both in the gaseous state and 

 dissolved in water. 



On the 24th of May, the following results were observable. With one 

 exception, the plants in Nos. 1 and 2 had attained to a fair size, and looked 

 healthy ; and, with two exceptions, the same may be said of the plants in 

 Nos. 3 and 4; all the plants were in flower. In No. 5 the result was differ- 

 ent; the seeds had germinated, and the plants grew favorably for a short 

 time, but, at the period above mentioned, presented small, sickly, and de- 

 caying haulms, and no appearance of flowers. 



On the 12th of July the plants to which the nitrogenous substances were 

 supplied had perfectly matured their seeds, whilst those grown with the 

 non-nitrogenous manures had withered away, after attaining a stunted stat- 

 ure, and without having made any attempt at maturation. I may here 

 remark that the peas grown under the circumstances thus described were 

 not what would be considered good by a market gardener, and there was 

 but a poor return for the seed. My object, however, was not to grow a good 

 leguminous crop, but merely to endeavor to extend our knowledge of the 

 nature of the food of plants. 



Some of the plants straw and seed grown in Nos. 1 and 2, were ana- 

 lyzed, and were found to yield an amount of nitrogen, which, compared to 

 that contained in the original seed, was as thirty-eight to one. The nitrogen 

 in the plants grown in Nos. 3 and 4 was found to be greater in quantity, in 

 the proportion of thirty -four to one, than that contained in tiie original 

 seed. This increase, which could only have been derived from the nitrogen 

 in the yellow prussiate of potash and nitrate of potash, proves that these 

 substances should be added to the list of materials capable of being used as 

 a nitrogenous food by plants. 



I intended to try some experiments this year with reference to sulpho- 

 cyanide of potascium and uric acid, as sources of nitrogen for plants, but 



