No. 4.] NITKOGEX AND FERTILITY. 179 



moist soil being far better than a dry one. Tiie organisms 

 must have air, or they soon die ; hence the importance of 

 thorough working of the soil, both to admit air and con- 

 serve soil moisture. Direct sunlight is fatal to the cultures, 

 but probably has no effect after they are introduced into the 

 soil. Soil acidity is unfavorable to the growth of these 

 organisms ; hence the addition of lime or ashes to a soil is 

 an advantage, and is often a necessity for the formation of 

 root nodules. In experiments at the Maine station it has 

 been found difficult to grow root nodules upon alfalfa, with- 

 out the use of very considerable quantities of lime or ashes, 

 on soils that grow clover or peas luxuriantly and with abun- 

 dant nodules. This would seem to indicate the possibility 

 of these organisms adapting themselves to different condi- 

 tions as regards soil as well as host plants. 



Depart^eent of Agriculture Cultures. 



The failure of nitragin can be attributed to the method of 

 growing and keeping the cultures. It was found that when 

 grown with an abundance of nitrogen the bacteria speedily 

 lost the power of acquiring nitrogen. At the Department 

 of Aoriculture the cultures are o-rown in media that contain 

 no nitrogen, and the claim is made that thus grown the 

 bacteria have increased virulence over the original stock. 

 Nitragin was sent out in liquid form. The department pre- 

 pared dry cultures for shipment. They saturate absorbent 

 cotton in a lif(uid culture of the nodule-forming organism, 

 and then carefully dry the cotton. In this way millions of 

 bacteria are held within a very small amount of cotton, and 

 they remain dormant, much as seeds, waiting for the proper 

 conditions to revive them. For use this dry culture is im- 

 mersed in water, to which proper chemicals (sugar, mag- 

 nesium sulphate and potassium phosphate) have been added 

 for food. After they have grown for twenty-four hours in 

 this solution, a little ammonium phosphate is added to still 

 further increase the growth. The process has been patented 

 by the department, but no restriction is placed upon the 

 manufacture of cultures by these methods, provided they 



