32 THE DEVELOPMENT OF KAW COTTON 



(Fig. 4), until the food formed during the day is exhausted, 

 which may happen before the morning if the previous 

 day's experiences have been very severe, though this 

 does not appear to be often the case in good cultivation. 

 The total growth in the twenty-four hours thus depends 

 mainly upon the temperature at night, with modifications. 

 The chief of these modifications are growth in the morn- 

 ing after sunrise, due to milder weather ; and overheating 

 during the day, which poisons the cells and slows growth 

 during the following night (Fig. 4). 



Lastly, of the three main controlling factors of growth, 



we have, in addition to temperature and water, the soil 



itself. In so far as texture is concerned, it 



Suitable ^ g easv ^ o rea( j from the foregoing discussion 



the reason which makes loam the most suit- 

 able soil for cotton namely, free movement of water to 

 the root system, superadded to ample retention of water 

 by the soil particles. There is a second reason, which is 

 that cotton roots appear to be intolerant of any deficiency 

 of air for their respiration (probably for reasons connected 

 with those discussed) such as may easily happen in a 

 clayey soiL 



Besides the texture of a soil, its depth and its composi- 



tion have to be considered. These two go partly by inverse 



proportion. A large plant will flourish in a 



pacing o sma Q pot o f rich SO Q or j n a l ar g e p O t of poor 



the Plants. f 



soil; but the daily water-strain on cotton- 



plants makes a large volume of soil essential for the best 

 results, unless unceasing watering can be given in driblets, 

 which is not practicable in the field. A large volume of 



