86 MASSACHUSETTS HORTICULTURAL SOCIETY. 



abnormal in respect to food supply or access of nitrogen com- 

 pounds or otherwise. In those which seem most conclusive 

 against the assimilation of free nitrogen the arrangements were 

 such as maj^ have hindered the action of electricity if not that 

 of nitrogen-fixing micro-organisms, two agencies towards which 

 late research points as possible, if .not certain, factors in the fixa- 

 tion of nitrogen. In all there is the possibility, and in some a 

 very strong probability, that the results may have been affected 

 by liberation of nitrogen from seeds or plants or food supplied — 

 a liberation which is sometimes, if not always, due to ferments. 

 This may materially reduce the nitrogen found at the end of the 

 experiments, and with it the apparent gain of nitrogen from the 

 air. The evidence from the field against the assimilation is of 

 necessity more or less incomplete, since — to say nothing of 

 other difficulties — some of the important factors of the problem, 

 such as the acquisition of nitrogen b}' the soil and its liberation 

 from the soil, are inadequately settled or left entirely out of 

 account. And, finally, to deny the acquisition of atmospheric 

 nitrogen is to leave some of the most evident facts of production 

 unexplained. 



On the other hand, the evidence in favor of the acquisition of 

 nitrogen b\' plants, legumes especially, from the atmosphere during 

 their period of growth, is direct and positive. In pot experi- 

 ments the gain has been at times very large, and in comparative 

 trials it has been larger or smaller in proportion as the conditions 

 have been more or less nearly normal. Less accurate, but at the 

 same time very strong, evidence in the same direction comes from 

 experiments in the field. The conclusion that plants acquire 

 atmospheric nitrogen accords with and explains facts of vegeta- 

 ble production otherwise unexplained. And late research leads 

 us to hope that the explanation of the processes b\' which the 

 nitrogen is acquired may be found, perhaps, in the near future. 



It is reasonably certain that the combined nitrogen of the 

 atmosphere is assimilated by plants. If the results of research 

 should continue to develop in the same direction in which they 

 have been developing of late, it will require but a short time to 

 place the assimilation of free nitrogen beyond question. Unless 

 future research should bx'ing evidence directly opposed to the best 

 now at hand, it must be allowed that the greater part of the nitro- 

 gen which tlje plants obtain from the air comes through the foliage. 



