271 



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.The critic adds, however, that this article is a welcome addition 

 to our store of facts in reference to the much discussed question 

 of the manner of cell growth. E. L. G. 



Uji the Origin and Behavior of Nitric Acid in Plants. B. Frank. 

 (Ber. d. d. Bot. Ges.. v., 472-487.) 



-I he author, in the first place, discusses the theory prevailin 

 in vegetable physiology, according to which the nitrates taken 

 up by the plant from the soil are conducted upwards into the 

 Jeaves, where they are utilized in the formation of ortjanic nitro- 



cr 



t3 



th 



gen compounds, which, in their turn, migrate back to the points 

 at which they are consumed. The facility with which the osmosis 

 oi the nitrates takes place, and the actual occurrence of saltpetre, 

 seemed to justify this opinion. From the fact that nitric acid is 

 mostly found in the greatest proportion in roots and stems, di- 

 nimishing toward the leaves, in which it is either not present at 

 ^h or in only very small quantities, and from its total absence from 

 the parenchyma of the leaves, it has been concluded that its 

 assimilation must take place in the green cells of the leaf. The 

 absence of nitric acid from the branches of shrubs and trees some 

 have sought to explain by assuming that these plants do not 

 n^eet with any nitrates, but only with ammonium compounds, in 

 e deeper layers of the soil to which their roots penetrate. 

 On the other hand, Liebig's opinion that the ammonia of the 

 soil is the only source of nitrogen available to the plant for assim- 

 nation has, of late, found new advocates. Berthelot and Andre* 

 determined the relative amounts of nitric acid in the soil and in 

 plants grown on it, and found, e. g., in Amarantus gigafiteus, 

 320 kg. of saltpetre per hectar, while the soil itself could not 

 have furnished more than 54 kg., in which calculation, however, 

 ^ investigators did not consider the stony subsoil. Still they 

 assume that in the tissues of the stem a nitrification of the ammo- 

 nia, or even an oxidation of free nitrogen, is taking place. 



The author then proceeds to give the results of his own in- 

 vestigations. The best reagent for nitric acid was found to be 

 tliphenylamin — sulphuric acid— which is the only one producing 

 3 distinct blue coloration. AH the seeds examined, of plants be- 



th 



* 



Compt. rcud., XCVIII., No. 25. and XCIX.. Nos. 8-17. 



