166 American Horticultural Society. 



ticular fermentation, is present in all fertile soils, and really constitutes one 

 of the factors of fertility. 



5. Plants do absorb assimilable nitrogen by their leaves (ammonia) ; but 

 the most of this food element is taken into the plant through the roots, and 

 hence from the soil. 



These things, as has been stated, are conclusions reached through the most 

 patient and laborious experiments and investigations, the results of which 

 have often been, to all appearances, contradictory and, at the time, unex- 

 plainable. But at least some of the difficulties have been in late years re- 

 moved, and one comes to have much confidence in the conclusions reached. 

 Yet it is even now reported that a prominent American chemist finds that 

 plants under normal circumstances do absorb and assimilate free nitrogen, 

 and he accounts for the contrary statements by so many careful and skillful 

 experimenters, by supposing the test plants were not under natural condi- 

 tions, especially were not exposed to the atmospheric electrical currents as 

 were his own. 



The point which cultivators need most to observe is, that soils, in the or- 

 dinary processes of cropping, grow constantly poorer in the nitrogenous sup- 

 plies, for the amount of ammonia and nitric acid brought down by rain and 

 dew over the given area is much too small for the annual demands of thrifty 

 vegetation. No system of crop rotation or of green manuring can indefi- 

 nitely perpetuate the fertility of soil. The time must come, sooner or later, 

 when artificial application of nitrogen-forming material is a necessity for 

 continued luxuriance of plant growth. Were it not that there is such a con- 

 stant formation of assimilable nitrogenous compounds through the agency 

 of electricity, the world must soon become uninhabitable. Were it not for 

 the fermentation of dead organic matter through the agency of living organ- 

 isms, each of which requires a magnifying power of at least five hundred 

 times across to become visible to the human eye, there could be no crops, 

 such as we now depend upon. 



Under the most favorable circumstances, tillers of the soil ought to under- 

 stand how best to economize the nitrogen supply in soils, and this becomes 

 an imperative necessity in regions less favorably or fortunately situated. 

 With the knowledge now at command, man has it in his power to perpetu- 

 ate in this respect the priceless value of high fertility, or to vastly improve 

 upon the natural richness of soils in some localities. On the other hand, 

 from the want of knowledge or attention, he may soon set in operation great 

 natural phenomena whicii bring in their train poverty and barrenness— a 

 curse not only to one generation of human beings, but to the struggling 

 populations of future centuries, an inheritance of suffering and destitution, 

 instead of the helpful richness of our good Mother Earth when properly 

 treated. 



I will only add, here, that severe midsummer droughts, and especially upon 

 bare surfaces unprotected from the burning rays of the sun by a beneficent 

 screen of vegetation, followed at another time by deluges of water, are im- 



