M. Hosseus on the Nutrition of Plants. 225 



branes. Vessels of wood or of porous porcelain (unbaked), which 

 allowed the substances to pass through very slowly, also gave ex- 

 cellent results. The author obtained by this method, and fre- 

 quently in very beautiful forms, the sulphates of barium, stron- 

 tium, and lead, carbonates of barium and lead, oxalate of cal- 

 cium, borate and chromate of barium, magnesia, and the various 

 sulphides. In the hope of obtaining crystals of quartz, solutions 

 of alkaline silicates in porous vessels were placed in dilute acids, 

 and also exposed to the action of carbonic acid. Silicates under 

 these circumstances do not deposit gelatinous precipitates, but 

 white crystalline masses hard enough to scratch glass. These 

 crystals, however, were not quartz ; for they were soluble in alka- 

 lies, contained water and a small quantity of soda which seems 

 essential to their composition. The crystals from silicate of soda 

 contained 68 silica, 5 soda, and 27 of water in 100 parts. Neg- 

 lecting the small quantity of soda, the composition corresponds 

 to the formula Si0 3 + 2HO. 



The author's experiments furnish an elegant confirmation of 

 ChevreuPs view of the formation of crystallized oxalate of cal- 

 cium in the cells of plants ; for he succeeded in obtaining crys- 

 tals of this kind when he allowed a soluble calcium salt to act 

 through a membrane on a soluble oxalate. 



Hosseus has made* a scries of experiments on the influence 

 which various kinds of nutrition exert on the quantity of am- 

 monia and of nitric acid which plants contain. The plants taken 

 were the onion (Allium cepa) and the pea (Pisum sativum). The 

 amount of ammonia and of nitric acid in onions could not be in- 

 creased by corresponding mixtures of salts. The nitric acid 

 which they exhibit in summer has been produced by oxidation 

 of ammonia, and it is probable that in winter it again changes 

 into ammonia. The numbers show clearly that they cannot 

 assimilate nitric acid. While the roots, even of onions which had 

 only grown in a solution containing ammoniacal salt, contained 

 05 and 03 per cent, of NO 5 , the onions themselves gave 0084 

 per cent., the same quantity originally contained in them. Peas, 

 on the contrary, can assimilate both nitric acid and ammonia, 

 and more indeed than is necessary for their growth. In all ex- 

 periments it was found that the greater the quantity of ammonia 

 and of nitric acid, the worse appeared the growth of the plants, 

 and the smaller the harvest of completely developed seeds capable 

 of germination. Those which had grown in turf manured with 

 nitrates, furnished three times as great a crop as in soil treated 

 with ammonia salts. Manuring with both salts had no better 



* Arch. Pharm. vol. cxvii. p. 237. 



