$9 SOME ASPECTS OF THE INDIGO INDUSTRY IN BIHAR 
attention must be paid to thinning and selection. A good deal of natural 
selection takes place by the extinction, through poor soil aeration, of many of 
the deep-rooted constituents which naturally result from the gametic con- 
stitution of the crop. It is always found that many of the deep-rooted un- 
thrifty plants either die out altogether or lag behind the surface-rooted types. 
All small weak plants which survive should be destroyed from time to time, 
and the crop at flowering time should consist only of the type required, The 
best plants are those which branch copiously and which also flower early. 
After flowering has set in, a final thinning is required to eliminate those indi- 
viduals which, although of suitable habit, show a tendency to flower too 
late. 
The result is a magnificent crop of seed which in good years weighs out 
well over half a ton to the acre. Even in the worst years at Pusa, the yield 
has not fallen below a quarter of a ton to the acre. The seed produced is 
heavy and well matured and far superior to anything produced elsewhere. 
It germinates strongly and evenly and the resulting crops do well. As the yield 
of seed varies considerably with the season, estates should hold about half 
their annual seed requirements in reserve so as to make up for any deficit 
in a yearof late floods. Indigo seed retains its germinating power for 
several years if thoroughly dried before storage in the air-tight seed bins 
devised by the Botanical Section at Pusa which are now on the market in 
India. 
This improved method of seed growing has been successfully adopted on 
several of the indigo estates in Bihar and during the present year 1919, ex- 
cellent crops are to be seen, August sowing in Bihar will by itself improve 
the type of indigo as it helps to eliminate the deep-rooting unthrifty types sus- 
ceptible to wilt and favours the shallow rooted quick growing wilt resistant 
forms. Hence the importance of producing all the indigo seed required in 
Bihar itself and the discontinuance of the practice of importation from outside 
sources where natural selection does not operate to anything like the same 
extent. 
Il. THE GROWTH OF JAVA INDIGO. 
While the investigation of the wilt disease and of the factors underlying 
seed production were in progress, attention has been devoted to the conditions 
necessary for the growth of the ordinary indigo crop. A large amount of 
work has been done on this side of the question and several improvements in 
cultivation have resulted. The growth of the indigo crop, other things being 
equal, has been found to depend mainly on two factors—soil aeration and 
organic matter, 
