6o SCIENCE PROGRESS 



cakes. It has been shown by Rawson that these actions do 

 not destroy the indigotin, but only the impurities, so that 

 the indigo-cake becomes sHghtly richer in its percentage of 

 indigotin. 



Lines of Research. — Whereas the production of synthetic 

 indigo blue demands investigations of a chemical nature it is 

 obvious that the preparation of the natural dye necessitates 

 work in a wide range of sciences. 



Agricultural problems are met with in connection with the 

 growth of the plant involving both cultural and manurial 

 conditions. With these are closely connected botanical con- 

 siderations as to the type of plant and its fertilisation and 

 bacteriological problems in connection with the soil and root- 

 nodule bacteria. The place of the indigo plant in a rational 

 scheme of crop rotation is also a point of much agricultural 

 importance. 



Indigo is fortunately free from any serious fungal or 

 bacterial disease, the disastrous wilt having been shown to be 

 connected with the soil conditions rather than with any specific 

 organism. Weakly crops, however, suffer severely from an 

 insect pest, psylla. 



In the mahai, or fermentation process, there is much room 

 for the study of the bacterial and enzymic changes which 

 normally result in the production of indoxyl, but may if allowed 

 to proceed too far result in its destruction. 



Finally, the nature of the end-product, indigo cake or paste, 

 has to be considered with special relation to the possible 

 market. 



The investigations carried out have naturally been of a 

 complex nature, on the borderland between two or more of 

 the recognised sciences, so they will be considered from the 

 standpoint of the crop or process rather than that of the 

 sciences concerned. 



Agricultural Conditions. — Formerly indigo was grown by 

 planters on land specially leased for the purpose, and owing to 

 expiration of leases and new takings the land actually under 

 indigo in Behar was constantly changing. At present indigo 

 is not such a paying crop as it was, and the planters grow other 

 crops as well, the seet forming an excellent manure for cereals 

 such as wheat and oats. Indigo, being a leguminous plant 

 with nitrogen-fixing bacteria in root-nodules, brings about an 

 increase in the soil nitrogen. In order that the bacteria may 

 carry on this fixation, air must have free access to the roots, 

 and the aeration of the soil is accordingly of even greater 

 importance than for other plants. Thus, both on account of 

 the supply of seet and of the roots left in the ground, indigo 

 occupies the place of a nitrogen-enriching crop in the rotation. 



