122 THE CANADIAN NATURALIST. [-^pril, 



-water, and absorbable by porous bodies such as vegetal mould. It 

 is, therefore, readily washed down from the air by the rain and 

 dew, and as readily imbibed by the soil, and retained within its 

 bosom by the peculiar physico-chemical force, already referred to 

 as " surface-action." All fertile soils contain abundance of am- 

 monia thus availably presented for absorption by the roots of plants. 

 The leaves of plants also absorb ammonia from the air in quanti- 

 ties varying with the different genera and species. 



It is not only however in the form of ammonia that atmos- 

 pheric nitrogen is supplied to plants. Nitrogen combines with at- 

 mospheric oxygen to an extent always appreciable, and much aug- 

 mented under certain circumstances (as, for instance, during light- 

 ning-storms), to form nitric acid; which is washed down to the 

 soil by the rain, and assists, certainly by its solvent powers, prob- 

 ably also as aliment itself, in the nutrition of plants. Nitric acid 

 also originates to some extent, as a secondary product of the decay 

 of nitrogenous organic matters ; these yielding ammonia, which 

 oxydation converts into nitric acid and water. Furthermore, a 

 nitrogen-compound, containing both hydrogen and oxygen, viz. 

 nitrite of ammonium, has been lately ascertained (by Schonbein) 

 to originate during the slow oxydation of phosphorous ; two equiv- 

 alents of atmospheric nitrogen taking up two equivalents of water 

 to produce it. Nitrite of ammonium is similarly generated (ac- 

 cording to Kolbe and Bottger) during the oxydation of hydrogen, 

 and of hydrocarbons generally. Indeed there is fair reason to sur- 

 mise that the generation of this salt accompanies all processes of 

 slow oxydation ; such as, for example, that of humus in the soil. 

 These facts are of the deepest interest ; and should the supposed 

 universality of this natural reaction, as a concomitant of slow oxi- 

 dation, be confirmed, a powerful light will be thrown on the nature 

 and source of the nitrogenous alimentation of plants. It will in- 

 deed be a remarkable discovery, as Liebig (who cites these facts 

 in his admirable work above mentioned^) justly observes, should 

 it be found that the very process by which carbon is rendered 

 available as plant-food, operates also to bring atmospheric nitro- 

 gen into a form in which it is assimilable by plants. f 



* This view of the origin of nitrous acid and ammonia from atmos- 

 pheric nitrogen does not belong toSchonbien, but was previously enun- 

 ciated by Mr. Sterry Hunt (Canadian Journal, April, 1861). See also 

 Nickles, Silliman's Journal [2J, xxxv, 263-271. 



t " The Natural Laws," &c., pp. 326-328, Eng. ed. 



