198 MASSACHUSETTS HORTICULTUKAL SOCIETY. 



to be excellent plant food. Another good reason is that, of all 

 the elements, nitrogen is the one most nnwillingl}- forced into 

 chemical combination ; there is not another clement of common 

 occurrence that is so well satisfied to remain alone by itself as 

 nitrogen is. Very powerful chemical persuasion has to be brought 

 to bear upon it, to get it out of its state of isolation ; never was the 

 most confirmed old bachelor more obstinate in maintaining his 

 bachelorhood. It would be singular, indeed, if the plant, while 

 feeding as to everything else on chemical compounds onl}', should 

 have the heavy work put upon it of forcing unwilling nitrogen into 

 combination. It is evident enough from all our experience that it 

 does not do that work if it can get nitrogen elsewhere — and there 

 is not a particle of reliable proof that it does that work under any 

 circumstances whatever. 



Other chemists in France have investigated this question on a 

 small scale, but with contradictory results. There is not time to 

 speak further of their work. But I must give a brief account of 

 the experiments made b}- Professor Atwater, of Connecticut, within 

 the past three or four years. These were made with peas, grown 

 in sand which had been completely freed from plant food by wash- 

 ing and strong heating, after which it could contain no nitrogen. 

 The plants were fed with solutions applied to the sand, containing 

 known quantities of all the nutrients required, including a certain 

 amount of nitrogen compounds. They were left in the open air, 

 except when necessary to put them under shelter to prevent them 

 from getting any unknown quantities of nitrogen compounds from 

 rain or dew. In all but one out of fifteen such experiments, car- 

 ried on in two successive years, there was a gain of nitrogen over 

 and above what was supplied in the seed and food. This gain was 

 in two cases fully equal to all that the plants took from the nutri- 

 tive solutions with which they were fed, and the plants, according 

 to the observations of the experimenter, seemed the better able to 

 make these gains, the more the conditions of their nourishment, as 

 to the quantity and kind of food supplied, were like those of ordi- 

 nary growth in the field. On the basis of his results, Prof. At- 

 water estimated that an acre of peas, fairly well fed, might gather 

 in, from some source other than the food supplied in the soil, from 

 70 to 120 pounds of nitrogen. It would require over 700 pounds 

 of nitrate of soda, costing about §19, to supply 120 pounds of 

 nitrogen. • 



