272 



longing to many different orders, contained absolutely no nitrates, 

 nor did their seedlings show any trace of it if the seeds were 

 caused to germinate in water free from saltpetre. Plants were 

 grown both in water containing no nitrogen compounds at all, 

 and in nutrient liquids with ammonium salts, instead of nitrates, 

 dissolved in them. AH the experiments proved conclusively 

 that no plants, not even the true "saltpetre plants'' (sunflower, 

 tobacco, Urtica, Amaranius, etc.), will ever contain any nitrate, 

 unless their roots have been in a position to receive it, and that 

 no plant has the power to form within itself even a trace of nitnc 

 acid, either in the light or in the dark. 



As to the distribution of the nitric acid in plants, the result is 

 reached that in typical, so-called saltpetre plants, much more 

 nitric acid is received during the period of vegetation than is 

 needed at the time being for the production of new organs. 

 The excess of the unchanged nitrate is stored in all those organs 

 which are available for this purpose, and as cells with large spaces 

 for cell-sap are especially well adapted to keep the nitrates in 

 solution, the parenchyma tissues of root, bark and pith, petioles, 

 and veins of leaves will serve for the temporary storage of the 

 nitrates, so that at the time when the fruit is ripening the sud- 

 denly increased demand for nitrogenous substance can quickly be 

 supplied. Even in plants which thus far were supposed to con- 

 tain no nitric acid (trees, yellow lupine, etc.), it is always found 

 in their roots, not, however, higher upwards, most likely because 

 it is soon assimikited into nitrogen compounds. 



The principal argument in favor of the theory that the assim- 

 ilation of the nitric acid must take place in the green leaf, in con- 

 nection with the formation of the organic carbon compounds, is, 

 as mentioned above, the observation that in many plants the 

 nitric acid can be demonstrated in the tissues as far as the veins 

 of the leaf, and then disappears. After referring to the fact that 

 in arboreous, and in a few other plants, no nitric acid at all is 

 found in the leaves, the author describes several experiments in 

 order to prove that there is no migration of the nitrates what- 

 ever, having the leaf for its terminus, and finally reaches the 

 conclusion that the nitric acid which is taken from the soil as 

 nitrogenous food is not assimilated in the green leaf-tissue, but in 





1 



