272 Professor J. Reynolds Green [Feb. 9, 



the sugar-cane. In its external appearance it cannot very well be 

 distinguished from either of the others. It consists again of a yeast 

 and a bacterium which are associated in the same way as are the 

 organisms in the gingor-beer plant. The yeast is not the same 

 as in the latter, and the bacterium differs in some respects, though 

 its structure and mode of behaviour are very much like those of 

 Bacterium vermiforme. It is a sheathed organism which seems to 

 have the power of casting the sheaths in the same way as has been 

 described. 



The result of the symbiotic fermentation is an effervescent 

 liquid of distinctly acid taste, which if the fermentation is not 

 prolonged makes a very pleasant beverage. If the action is allowed 

 to go on for several weeks the percentage of the acids becomes so 

 great that it is no longer possible to drink it. 



The morphological features of the organism resemble to a very 

 large extent those of the ginger-beer plant. A more detailed exami- 

 nation has been made of the products of the fermentation than in the 

 former case, and certain features of the symbiosis have been ascer- 

 tained. The organisms of which the plant consists can easily be 

 separated and independent cultures made of both, so that the separate 

 and conjoint fermentations can be studied. 



The yeast, when cultivated alone, produces alcohol and of course 

 carbon-dioxide, together with a little acetic and a little succinic acid. 

 In these respects it appears to differ very little from the ordinary 

 yeast of beer. 



The bacterium can form no alcohol, but it gives rise to the forma- 

 tion of much larger quantities of both these acids. Besides these, if 

 cultivated in solutions of cane-sugar it produces a very large quantity 

 of two hemicelluloses, which when in a certain excess, sink to the 

 bottom of the liquid and form a kind of gelatinous sediment. This 

 viscous matter can be precipitated by alcohol from its watery solution. 

 It appears to be the same material as the sheath of the organisms, and 

 it is noteworthy that when it is formed the organisms possess no 

 sheaths. The gelatinous substance is not the discarded sheaths of 

 the bacterium, but seems to be formed in the culture liquid at the 

 expense of the sugar. It is in fact a viscous fermentation of the 

 latter. 



If we compare the products of the fermentation of the two 

 organisms separately, those of the same two microbes when present 

 together in the same culture-fluid, but not in the symbiotic form, and 

 finally those of the conjoint organism, we find that there is evidence 

 of some subtle influence exerted by the one upon the other when they 

 are in complete symbiosis, though it is difficult to suggest in what that 

 influence consists. 



Comparing cultures of them both separately with one in which 

 both were present but independent, the nutrient medium being a 

 mixture of cane-sugar and fruit-sugar, less acid was produced in 

 jfche iatter case in the proportion of 224 to 1175. The same quan- 



