36 THE DEVELOPMENT OF RAW COTTON 



being ruled out by considerations of yield, it follows 

 that the soil must be deep. In respect of this our 

 ideas have undergone great changes since 

 1 90 8, in which year the author first traced a 

 cotton root to a depth of two metres below the surface. 

 This trifling episode led us to reconsider many matters. 

 Thus, in the event of surveying a new district for cotton- 

 growing, we are no longer content to examine the top 

 foot of soil, but we require to know something about the 

 state of affairs down to some 6, or even 10, feet below the 

 surface. Again, that a rise of the water-table which did 

 not reach within a metre of the surface should be preju- 

 dicial to the crop was no longer absurd, since this would 

 drown out half the root system of an adult plant, and, as 

 we now know, the portion which is doing most of the work 

 in the autumn. It had formerly been thought that cotton 

 was a comparatively shallow-rooted plant, on account of 

 the slenderness of the tap-root, which diminishes very 

 quickly in the first foot of descent, and looks as if it were 

 nearly at an end. This slenderness does not prevent 

 it from carrying large amounts of water, as we have seen, 

 the main water-conducting cell-elements being only two or 

 three in number, and consequently of wide bore. Through 

 these two or three tubes, not exceeding J millimetre 

 each in diameter (-^ inch), there rushes a stream of about 

 a litre of water during some ten hours. From th^ tap- 

 root arise laterals, which at first form a gossamer web 

 around the seedling tap-root, but which very largely die 

 down, only a few surviving, to be supplemented by new 

 ones lower and lower down. The survivors run out 



