66 SCIENCE PROGRESS 



course makes the process far more tedious and complex than 

 it would be, were it possible to deal with plants which are 

 readily self-fertilised. Furthermore, it does not follow that 

 the plants specially rich in indican would be vigorous and 

 give a high yield of leaf. Indeed, the plants raised at Pusa 

 from seed selected at Sirsiah were of a poor nature vegetatively, 

 but low vigour and high indican content are not necessarily 

 linked together, of course ; namely, it is unlikely that they are 

 coupled characters in a Mendelian sense. 



Percentage of Leaf as affected by External Conditions. — With 

 regard to leaf yield, Davis has shown that well-spaced plants, 

 which were delayed in their growth by a cover crop of wheat, 

 and subsequently grew rapidly after wheat harvest when the 

 rains came, were of a bushy form, and particularly rich in the 

 proportion of leaf to total plant. Thus this factor also is 

 largely modified by external conditions. 



From a consideration of the facts and opinions quoted 

 already, and from a general impression gained by perusal of 

 the reports of the research stations, it appears to the writer 

 that the chances are small that results of value are to be 

 obtained from selection work aiming at the production of a 

 variety specially rich in indican. Improvement is to be sought 

 rather in the selection of specially vigorous plants. 



Whether the natural indigo industry survives or dies out 

 depends upon soil and cultural conditions, and upon conditions 

 of manufacture. The possibility of improvement in the plant 

 is a secondary factor on account of the length of time which 

 must of necessity elapse before any results can be expected. 



As an item of practical interest, it may be pointed out that 

 were a hardy strain of indigo specially rich in indican to be 

 obtained, it would still be a matter of difficulty to grow it on 

 a large scale owing to the deterioration it would undergo in 

 the field through crossing with the type commoijly grown, the 

 pollen of which would be carried by bees. 



The Indigo Fermentation, or Mahai. — A very brief account 

 of this has already been given, and as yet it is not possible to 

 write a complete one, for much still remains to be discovered 

 as to the mechanism of the process. The recent work of 

 Davis, in conjunction with Hutchinson and Walton on the 

 bacteriological side, has, however, brought to light many points 

 of interest. When the water is run into the steeping-vats a 

 series of changes is initiated. It is necessary to see how far 

 these are due to autolysis in the plant and how far they are 

 induced by bacterial action. The above-named workers have 

 laid emphasis upon the importance of the latter. 



It has been shown that the duration of the fermentation 

 process depends upon the bacterial content of the water used 



