270 FORMATION OF SLIME OR GUM BY RHIZOBIUM LEGUMINOSARUM, 



In testing the gum of the Pea and especially of the Bean race, 

 it was noted that dilute sulphuric acid thickened or clotted the 

 mucilages. These were not so gelatinous as the gum* from the 

 Macrozamia organism, but the slime of that gum had been 

 acidified with dilute acid before being heated in the autoclave, 

 and the acidification probably accounted for the very gelatinous 

 na< ure of the solution. The Bean gum was tested with a few acids 

 to see if the kind of acid had an influence in producing the 

 insolubility. A drop of acid was stirred into a drop of the gum 

 and the effect noted. Clotting was obtained with sulphuric acid 

 (1-6), hydrochloric acid (1-4), nitric acid (1-4), phosphoric acid 

 (glacial), acetic acid (glacial), and oxalic acid (saturated solution). 

 A thickening was produced with lactic acid (concentrated). No 

 effect was obtained with acetic acid (1-9) or with saturated solu- 

 tions of citric, tartaric and succinic acids. During the hydrolysis 

 of these gums, it was noted that they were insoluble in cold 

 5 % sulphuric acid even when in contact with it for a day, but 

 they readily dissolved on boiling. The insolubility of the gum 

 in dilute acid is probably a factor in causing the formation of the 

 long filaments which are seen stretching from cell to cell in the 

 nodules of the roots of the Leguminosce. From these experiments 

 with acids, one might be justified in inferring that the acidity of 

 the juice of the nodules is due, in part at least, to oxalic or to 

 mineral acids which are possibly liberated from manurial salts 

 through the withdrawal of the base necessary for the formation 

 of tissue. 



The gum of the Macrozamia race was more fully examined than 

 the gums of the other races, partly because the slime was pro- 

 duced in greater abundance and partly because the gum remained 

 transparent during the various coagulations with alcohol. It 

 was easily hydrolysed with 5 % sulphuric acid, and during the 

 hydrolysis, furfural was detected in the aerial condenser. Two 

 osazones were obtained; one, present in relatively much greater 



* A solution containing 1*6% of the crude gum gave a jelly of the same 

 consistency as a 1 % solution of gelatine. 



