BY R. GREIG-SMITH. 267 



Although the composite bacteria are found in great numbers 

 in the nodules, they are not limited to these places. Moore 

 found several instances of luxuriant vegetable growth without 

 nodule formation, and upon microscopical examination detected 

 rhizobial forms within the tissues of the root. I have isolated 

 and grown them from the stems of the lupins quoted above. As 

 they apparently occur throughout the tissues of the plant, one 

 may ask, What is the significance of the nodule 1 This will be 

 indicated in the research. 



When taken directly from the nodule the bacterium may or 

 may not produce a visibly slimy colony. This is notably the 

 case when glucose-gelatine plates are used. As a soluble carbo- 

 hydrate is essential, slimy colonies are not to be expected upon 

 media containing no sugar. But even with a suitable medium, 

 such as saccharose-potato-agar,* saccharose-bean agar,f or maltose- 

 meat-agar,| I have found that the bacteria from some plants 

 produce a relatively luxuriant slimy growth, while from other 

 plants the microbes grow as a rather dry, loose film. It is 

 possible in some cases, by subcultivating every two or three days, 

 to cause the latter races to increase their slime-production, but 

 in other cases such a recovery of power did not occur. Evidently 

 some races are capable of producing slime abundantly and others 

 are not. 



As a rule, one can tell from the luxuriance of the original 

 colonies whether or not the bacterium can be classed as a good 

 slime-former. The races that formed slime to some exte*nt were 

 retained after isolation, for they gave material to work upon and 

 products which could be measured under varying conditions of 

 nutrition. The races from Krai did not produce slime at first, 

 but they were induced to do so by frequent subcultivation for 

 about a month upon saccharine media. 



* Saccharose 20, glycerin 10, potato juice 250, agar 20, tap-water to 1000. 



+ Saccharose 20, bean extract 400 (250 grm. chopped French Beans, boiled 

 for an hour in 1000 c.c. of tap-water, strained, squeezed, filtered and made 

 up to a litre), agar 20, water to 1000. 



t Maltose 20, agar 20, meat extract 500, water to 1000. 



