RECLAIMING LOST NITROGEN 139 



these dwellings tubercles or nodules. It matters not 

 what the name is : the work accomplished is the matter 

 of consequence. These nodules are often very large 

 as large as a pea. And then again they are small as 

 small as a pin head. Just as soon as these nodules or 

 tubercles were associated with bacteria and bacteria with 

 nitrogen fixation, many experiments resulted in conse- 

 quence. The result of these investigations led to the 

 solution and the explanation by Hellriegel and Willfarth 

 in 1888 of this knotty problem : they told how free nitro- 

 gen is fixed in the soil. 



A word about these bacteria. These little plants are 

 real bacteria: thread-like bodies that send their advance 



scouts throughout the roots, 

 into all tissues of the roots. 

 Bacteriologists tell us that 

 these bacteria are not just 

 like other bacteria. They dif- 

 fer in some ways from all the 

 other kinds. They seem to 

 belong to a class of their own 

 in methods of growth and 



ROOT TUBERCLE BACTERIA development. In reference to 

 (AFIER MAZE) them, Conn, a noted bacteriol- 



ogist, has this to say : "At 



certain stages of development, by branching or budding, 

 they produce what are called Y and T forms, a method 

 of growth not characteristic of bacteria, in general. It 

 is found, also, that after the beginning of the formation of 

 the tubercle, long, thread-like masses, filled with bacteria, 

 can be seen extending among the tissues of the plant. 

 The long threads appear almost like pouches in which 

 the bacteria are held, but they eventually disappear and 

 the bacteria themselves diffuse through the tissues. 



