8 SOME ASPECTS OF THE INDIGO INDUSTRY IN BIHAR 
in April, but does not become intense till the soil is cooled and moistened by 
the early monsoon rains in May when the numbers formed are very large. 
As would be expected, these bodies are much more abundant in the first four 
inches of soil than in the deeper layers. No further changes occur till the 
first cut is taken, Cutting back is followed by the destruction of practically 
all the fine roots and of most of the nodules. Before new growth can take 
place, root regeneration is necessary. The extent and speed of this regener- 
ation is found to depend on the aeration of the soil. If the rainfall is low and 
if the levels of the rivers and wells do not rise to any great extent, as in 1919, 
the fine roots and nodules are rapidly renewed. Thus in the case of the root 
systems of three plants exposed on June 14th, 1919, 194 nodules were found 
on the upper laterals. These were removed and the soil quickly replaced. 
A month later, the roots of these plants were again exposed and numerous 
new fine roots and no less than 942 fresh nodules were found. The reaction 
of the roots to alterations in the soil atmosphere during the rains is very 
striking. After the middle of July and at the beginning of September of the 
present year, 1919, when heavy rains, combined with the rise of the ground 
water, adversely affected the aeration of the soil, an immediate root response 
to the changed soil conditions took place. The fine roots in the deeper layers 
of soil were quickly killed, new roots were only formed near the surface of the 
ground while the finer branches of the upper laterals were found to exhibit 
marked aerotropism and to bend upwards towards the air. This continued 
on both occasions till a break in the rains and a fall of the ground water restored 
soil aeration when normal root development again ensued. During the late 
rains, the formation of fine roots and nodules is almost always restricted to 
the upper four inches of soil. At this time, the lower regions of the tap-root 
and the lower laterals are practically devoid of nodules and small roots and 
the current of crude sap is maintained entirely by the fine roots near the surface 
of the ground. This is effective while monsoon conditions prevail but when 
the rains cease and the upper layers of the soil dry, the plants either become 
wilted or else shed their leaves and pass into a resting condition during the 
cold weather.'| Root and shoot growth are resumed when the soil tempera- 
ture rises in March. 
In the case of Java indigo sown for seed in August, the feature of the 
root system is the development of abundant nodules on the upper roots during 
late September and October. These, however, become absorbed during 
* Mulching the soil to prevent the loss of moisture acts as a preventative of wilt during 
October, November and December. 
