314 



SYMBIOTIC NITROGEN FIXATION 



entrance into the roots. Small quantities of nitrates tend to 

 stimulate. 



Legumes Associated with Non-legumes. For centuries it has been 

 the practice in China, Japan, Western Asia, Northern Africa, as well 

 as ancient Rome, to grow legumes and non-legumes in combination 

 and there is no doubt that time and again practical farmers have 

 noted the more vigorous growth and darker green of non-legumes 

 when so grown, long before the investigations of Hellriegel and his 

 associates established the fact that leguines are capable of utilizing 

 atmospheric nitrogen. His discovery gave the key to the mystery, 



FIG. 42. Double pots used in showing influence of Legume on non-legume. 

 (After Lipman). 



the non-legume was getting combined nitrogen from the legume. 

 This was strikingly demonstrated by a very ingenious experiment 

 conducted by Lipman. He grew non-leguminous plants in soil in 

 a porous pot surrounded by earth in a larger glazed earthenware pot 

 in which leguminous plants were growing and found that under 

 favorable conditions non-legumes associated with legumes may 

 secure large amounts of nitrogen from the latter. This power of 

 supplying nitrogen to non-legumes varies <tyB? different legumes. 

 At times it may appear as an increased yield, whereas at others it 

 may appear as an increased proportion of nitrogen in the dry matter 

 of the non-legume or both. The following table gives the per- 



