290 FORMATION OF SLIME OR GUM BY RHIZOBWM LEGUMINOSARUM, 



While this may be true generally, it cannot be relied upon, as is 

 shown by the isolation of three distinct races from a single nodule 

 of the Blue Lupin. We cannot say with certainty which of 

 these races is typical for the species or for the individual plant in 

 the nodule of which they occurred. Race (a) or (b) was more 

 numerous, but that may not be a criterion. Upon theoretical 

 grounds, I should rather trust to the acidophile race (d). The 

 isolation of at least three races in one nodule raises the questions, 

 Which of these is most akin to the original microbe that entered 

 the root-hair 1 and, If such an alteration can occur in the nodule, 

 is there a microbe specific for any species or genus of plant 1 

 Remembering the case of Bad. acacice and its variety Bad. 

 metarabinum, I am of the opinion that the differences which are 

 found among the races after isolation are largely the result of 

 the sojourn of the microbe in the sap of the host-plant. 



The plant is probably able to modify the faculties of a Rhizo- 

 bium derived from any other plant to its individual requirements, 

 once the bacterium has obtained access to the tissues of the root. 

 But if the micro-organism cannot form slime from a particular 

 sugar and only that sugar chances to be in the sap of the plant, 

 there can be no inducement offered to the microbe to enter the 

 root-hair. Bacteria from one plant are therefore best adapted 

 for entering into symbiotic relationship with members of the 

 same genus, as it is only upon plants of the same kind that we 

 can rely for containing the sugars to which the microbe has been 

 accustomed. 



Conclusions. 



It has been shown that slime is formed by the majority of the 

 races of the nodule-former upon solid media and that as a rule 

 the media need only contain a sugar and a source of nitrogen, 

 the traces of salts such as occur in the infecting material, the 

 nutrients and the tap-water being enough for their requirements. 

 In such media, growth could not be maintained for any length of 

 time, but this could not be expected. 



The quantity of slime that may be produced depends largely 

 upon the combination of nutrients, and especially upon the nature 



