108 SCIENTIFIC REPORTS OF THE AGRICULTURAL RESEARCH 



further confirmation of the importance of bacterial action- 

 in indigo manufacture. 



It has been shown that the failure in factory practice 

 to obtain nearer approximation to the theoretic yield of 

 indigo from the plant is due to several factors of which the 

 following have now been found to be of importance : — 



(1) Destruction of indican in the leaf during fermen- 



tation or steeping. This appears to be due to 

 several causes all preventing the desirable 

 change of indican by hydrolysis into indoxyl. 

 These probably include the action of plant 

 enzymes and bacteria other than those producing 

 indoxyl from indican. With this source of loss 

 may be associated 



(2) Incomplete extraction of the indican, as although 



no residual indican may be found remaining in 

 the plant after steeping, yet investigation has 

 shown the very strong probability that its 

 absence is due not to removal into solution in 

 the steeping water but to actual destruction or 

 decomposition in situ. This destruction appears 

 to be due partly to enzymic and partly to 

 bacteria] activity other than that resulting in 

 production of indoxyl. 



Control of the fermentation taking place in the steeping 

 vats must therefore take the form of introducing conditions 

 which will minimize such losses, probably on the following 

 lines :— 



(1) Promote rapid extraction and so remove the 



indican from deleterious surroundings in the 

 leaf tissue. 



(2) Promote rapid hydrolysis and so lessen the period 



of time during which the indican in solution is 

 liable to conversion into products other than 

 indoxyl. 



Extraction. Until the hot water extraction previously 

 suggested as the most satisfactory method has been shown 

 to be practicable on a factory scale, it seems necessary to 



