392 BOARD OF AGRICULTURE. [Pub. Doc. 



He planted first a grain and then a leguminous crop, 

 manuring only with potash and phosphoric ac-id, and suc- 

 ceeded in every case in obtaining a good average crop of 

 grain. He felt convinced that the leguminous crops took 

 their nitrogen from the air, and spoke of the root nodules 

 they contained. 



With this l)rief historical description, let us return to 

 Professor Hellrieo-el's* work. In the year 1(S<SB, at a meet- 

 ing of German aaricultural exiieriment station workers at 

 Bremen, he l)r()ught forward the results of several years' 

 experiments, and proved conclusively, for the first time, 

 that the legumes were actually capable of utilizing the free 

 atmospheric nitrogen. 



By way of illustration, I present here a very brief outline 

 of how his work was carried out : — 



In one series he cultivated l>oth legumes and grains in 

 pots containing })ui'e sand. Both pots and sand were 

 ' reviously heated very hot, to destroy any nitrogen-con- 



iiiing organic matter, and all germ life. These plants 

 only grew to a certain height, and then turned yt'llow and 

 gradually died, though they were suj)plied with all the 

 fertilizing ingredients necessary to their growth exrepl 

 nitrogen. The plants and roots, both carefully collected, 

 weighed and analyzed, were found to contain only the 

 amount of nitrogen contained in the seeds. 



In a second series he omitted to sterilize the sand and 

 pots. After the grains and lupines had used \\\) all the 

 nitrogen of the seed, their leaves turned yellow and they 

 began to dry up. KSuddenly, within two or three days, it 

 was observed that the leaves on some of the legumes becuune 

 a ))riuht irreen a<;ain : the ])lants beiran to ijrow raijidly, and 

 tinally blossomed and produced seed. Little nodules were 

 also ()1)s('rved on the roots, and it was noticed that these 

 nodules began to a|)])ear at the same time that the plant 

 began its second growth. The grains in this series turned 

 yellow after they had used up the nitrogen in the seed, and 

 (lid not recover themselves. 



In a third series both the grains and the legumes were 



* llellrieicer.s orii^inal work ciiii l)e found in tlio Beilagelicft zurder Zeitschrift des 

 Vereiiis f. d. Kiibenztickcr-lndustrie d. D. 11., November, 1888. 



