170 BACTERIA AND THE GUM OF LINSEED MUCILAGE, 



the gum, but the alteration of a bacterial gum while in the tissues 

 of the plant would be extremely difficult to prove, for it is only 

 by the stability of the bacterial product that we are enabled to 

 trace the relationship. Yet it requires no great stretch of 

 imagination to believe that such an alteration of gum is probable. 

 If the transmutation of the carbohydrates and the alteration of 

 oil into carbohydrates are admitted, why not also admit the 

 conversion of bacterial gums ? 



The alteration of the functional activity of a bacterium raises 

 the question of the relationship of the gum bacteria. Was there 

 originally one species which has become so modified by different 

 plants that it appears as many 1 The determination of a bacterial 

 species depends largely upon the growth-characters, and as these 

 are influenced by the nature of the matrix in which the cells are 

 imbedded, it follows that the matrix or gum plays an important 

 part in determining the species. No two bacteria could be more 

 different in their cultural characters than JBact. acacice and Bad. 

 metarahinum, yet these are varieties of the same organism, pro- 

 ducing gums of different solubility. Another example is Bac. 

 Atherstonei, which forms a soluble or an insoluble gum. A 

 difference of colour-character is met in Bac. pseudai'ahiiius, which 

 may produce a yellow or a white colony. What may be called 

 the bacteria of the vegetable gums, i.e., those whose gums are 

 hydrolysed to arabinose or galactose, are similar in size, in 

 motility, in flagella, in the absence of spores, in being negative 

 to the Gram stain, and in slowly liquefying gelatine. As it is 

 chiefly, if not only, in the nature of the gum-product and in the 

 characters, which this involves, that the bacteria of this group 

 vary, there is a strong probability that they had one common 

 origin, and that the forms in which we find them, are due to the 

 transmuting action of the host-plants. This group of bacteria 

 contains organism "a." Even before the products of the bacteria 

 had been examined, I was led to the belief from the comparative 

 variety of the races and of the species of bacteria as well as the 

 comparative numbers present in the tissues of the plant, together 

 with the variable reactions of the samples of Linseed gum, that 



