FROM THE AIR BY THE LEGUMINOS^ 4I 



These bacteroids may be dissolved by ferments secrc'.ed 

 by the plants, and may even injure the plant should they 

 attain abnormal proportions. 



The plant thus makes use of the products of the bac- 

 teroids up to a certain point of its growth. ' The action of 

 the latter diminishes at thv-^ period of fructification and 

 eventually ceases. The bacteroids may revert to their 

 original condition. 



Formation of Races of Bacteria belonging to the 



Leguminos.-e. 



In view of these facts the question now arises whether 

 special races of bacteria are evolved belonging to different 

 Leguminosae. Opinion is divided. 



Eeijerinck shows that each of the Leguminosse possesses 

 corpuscles of distinctly different appearance : the dimensions 

 vary and their form is more or less branched. Should one 

 of the Leguminosag be injected with strange bacteria modi- 

 fications ensue which cause a variation from the original 

 type in the bacteria introduced. Laurent questions whether 

 these are not mere varieties. 



Maze divided the bacteria into two great classes : bac- 

 teria which are " calcophile," and bacteria which are " cal- 

 cophobe," i.e., adapted to alkaline and acid conditions in 

 the soil. 



Hiltner and Stormer split them into two groups : Rhizo- 

 hiiun radicicola and R. beijcrinckii. 



These classifications are by no means accepted by all 

 scientists. Some hold that the bacteria arise from a single 

 species, Pseudomonas radicicola, and merely show adaptative 

 race-differences. Others, such as Hiltner, believe that 

 the advantages accruing from culture of the Leguminosae 

 are the result of the action exerted by their roots round 

 about. The bacteria are in close relation with these roots 

 and convert soluble into insoluble nitrogen. 



