10 president's address. 



sooner or later to the conditions that occur within the root-hair 

 and the nodule. There are great differences in the facility 

 with which various races can produce slime under laboratory 

 conditions. As some races do not form it at all, there is reason 

 to believe thut the failure of trade cultures of " Nitragin " has 

 in the past been in part at least due to the fact that the import- 

 ance of the slime-forming function has not been recognised. 

 As they come from the nodules of various plants of the same 

 species, the bacteria may be similar, just as they may be similar 

 when taken from nodules of the same plant. But that such is 

 not always the case, was shown by three distinct races having 

 been obtained from a single nodule. The hypothesis has been 

 advanced that the plant utilises the intracellular albuminoids of 

 the bacterium for its nutrition. Dr. Greig-Smith has shown that 

 this is not probable, for although the great majority of the 

 bacteria and bacteroids are dead during the active growth of the 

 plant, they still stain deeply, and therefore cannot be in process 

 of solution. As the slime is nitrogenous, there can be no doubt 

 that the hypothesis advanced by Maze is correct, and that the 

 slime is the means by which the nitrogen is conveyed from the 

 bacterium to the plant. The inner structure of the betcterium 

 has given rise to much speculation, and latterly its sporangium 

 natuie has been advanced. Maze was the first to illustrate it as 

 consisting of coccobacteria within a branching capsule. The 

 Macleay Bacteriologist has shown that it consists of cocci within 

 a branching capsule, and is therefore allied to Leuconostoc and 

 Streptococcus. It has been shown that the most suitable 

 medium for growing the slime is one which approximates in its 

 nitrogen and^salt content to soil-water, so that, while the bacterium 

 is vegetating in the soil, the alkalinity and nutrients will sustain 

 the slime-forming function. The carbohydrates of the root-hair 

 are the chemotactic substances which induce the bacterium to 

 enter the plant. A second research showed that the bacterium 

 was capable of fixing atmospheric nitrogen upon synthetic media 

 under certain conditions. These also induced the formation of 

 slime. Races of the microbe which, while multiplying freely, 



