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SOME ASPECTS OF THE INDIGO INDUSTRY IN BIHAR 
tropical, as far as temperature is concerned, from March to November, but 
December, January, and February are too cold for the growth of this crop. 
When first introduced, Java indigo did exceedingly well, yielding heavy crops 
of leaf, rich in indican, as well as abundant seed. After some years, however, 
the plant began to show increasing signs of want of vigour and finally began 
to die of wilt during the second half of the ramy season. At the same time, 
the yield of seed diminished. The degeneration was progressive and by 1913, 
when we took up this investigation, many planters had already abandoned 
the cultivation while others had considerably restricted the area under this 
species. 
Wilt usually makes its appearance after the first cut during July and 
August, the severity of the attack depending on the season. Affected plants 
stand out clearly from normally grown individuals and are easily recognized 
in the field. At first, there is a slowmg down of growth while the foliage 
alters in appearance, the leaves become folded longitudinally and assume 
a yellowish-green, slaty colour. Leaf-fall is then rapid until only a_ tuft 
of stunted foliage is left at the tips of the branches. Afterwards, the 
plants die off in stages, the process taking place slowly, a branch at a 
time. 
A good deal of attention has been devoted by previous investigators to 
the cause of indigo wilt. Neither insects, fungi nor bacteria have been shown 
to be responsible for the trouble. Our investigations indicate that wilt 
results from the destruction of the fine roots and nodules under circumstances 
when regeneration is difficult or impossible. In the following pages, the 
evidence is recorded on which this conclusion is based. Before dealing with 
the actual observations and experiments, a brief reference to the chief factors 
underlying the cultivation of Java indigo in Bihar is necessary to bring out 
the significance of much of the following. 
I. Tue Factors. 
Soil. The soil of the Bihar indigo districts is a silt (often containing large 
quantities of finely divided calcium carbonate) belonging to the older allu- 
vium of the Gangetic plain. Its main characteristics, from the point of view 
of the indigo plant, are its depth, the uniformity of its fine particles, its water 
holding capacity during the hot months of April, May. and June, the com- 
parative nearness to the surface of the sub-soil water and the low content of 
oxygen in the deeper layers, as shown by the analyses of well-waters. The 
sub-soils often show rust coloured markings associated with green and blue 
