COBB'S DISEASE OP SUGAR-CANE. 



Lenses of high power show the gum to be swarming with microbes of the form known as bacilli 

 [fig. 2). When the gum is fresh and yellow in appearance, the microbes are all of one kind whose 

 features are well shown in the illustrations. * * * This microbe appears to be one not hitherto 

 described, and I propose to call it Bacillus vascular urn, in consequence of its occurrence in the vessels 

 of the sugar-cane. Each microbe has about it a small amount of gummy matter, which is a product 

 of its growth. The gum described above as issuing from the sap-vessels of the cane has, therefore, 

 two component parts, namely, microbes and a viscous gummy matter. This gummy matter appears 

 to be a new substance, and to it I have applied the name vasculin. 



This substance, which is probably made up of the bacteria themselves or of soluble 

 substances in great part derived from the outer wall of the bacteria, is described as follows: 



Vasculin, the substance formed by the growth of the Bacillus vascularum as it occurs in sugar- 

 cane, is a yellowish, non-crystallizable, viscid substance, having an almost imperceptible acid reaction. 

 The taste is that of a slightly soured solution of gum arabic. A short time after oozing out from the 

 ends of cut cane, by solution it converts ten times its weight of water into a fluid of the consistency 

 of mucilage as used for adhesion purposes. Though soluble in water it is insoluble in alcohol. The 

 addition of absolute alcohol to the raw substance converts it into a hard mass, but this is only owing 

 to the abstraction of water; on placing the hardened mass in water it soon resumes its former con- 

 sistency and appearance. Vasculin is not coagulated by alcohol. 



Watery solutions of the yellow exudate from the vessels of the cane were tested in 

 various ways. Lime-water precipitated it and the precipitate was redissolved on addition 

 of hydrochloric acid. The exudate was also precipitated by the hydrates of potassium, 

 sodium, barium, and strontium, but not by ammonium hydrate. All of the above precipi- 

 tates were redissolved by hydrochloric acid. Watery solutions were also precipitated by 

 lead acetate and ferric chloride, but not by ferrous sulphate, barium chloride, or silver 

 nitrate. The dissolved substance has little or no action on polarized light. The raw gum 

 contains only a slight amount of nitrogen. 



Badly gummed cane contains less sugar than very slightly gummed cane according to 

 the tests shown in table i. 



TABLE i. Analyses of Very Slightly and Badly Gummed Cane for Comparison. 



Some of the same chips were pressed by hand, and the juice thus expressed was tested 

 for sugar, with the following results : 



Per cent of cane sugar. 



Vrry riiftliUy gummed. 



14.90 



Badly gummed. 



1 1. JO 



The raw juice squeezed out by hand having stood 48 hours, was tested with decinormal 

 solution of sodium hydrate. 



The greatest care was taken that the two lots of canes subjected to analysis should 

 be strictly comparable in all respects other than the amount of gumming. 



