ATMOSPHERIC NITROGEN IO9 



gave as good results as the use of nitrogenous manure 

 for the wheat, but for many vears this fact was unex- 

 plained. 



/ /ZTn8. Hellriegel's Experiments. — He grew legu- 

 — Hiinous plants in nitrogen-free soils. One set of plants 

 was watered with distilled water, while another had in 

 addition small amounts of leachings from an old loam 

 field. The plants watered with distilled water alone 

 made but little growth, while those watered with the 

 loam leachings reached full maturity and contained 

 something like a hundred times more nitrogen than 

 was in the seed sown. The dark green color was also 

 developed, showing the presence of a normal amount 

 of chlorophyl. The roots of the plants had well- 

 developed swellings or nodules, while those that were 

 watered with distilled water alone had none. The 

 loam leachings contained only a trace of nitrogen. 41 



119. Experiments of Wilfarth. — Experiments by 

 Wilfarth give more exact data regarding the amount 

 of nitrogen taken from the air. Lupines were grown 

 in the same way, and one lot watered with distilled 

 water, while another lot received in addition leachings 

 from an old lupine field. 



Watered with distilled water. Watered with soil leachings. 



Dry matter. Nitrogen. Dry matter. Nitrogen. 



Grams. Gram. Grams. Grams. 



