THE CARBOHYDRATES PRODUCED IN CROPS 125 



cellulose persistently retain ash, some of which has probably 

 been in forms of partial combination. All forms of cellulose 

 on destructive distillation yield charcoal and a distillate 

 containing acetic acid and tar. As a rule, pure cellulose 

 yields from 30 to 40 per cent, of charcoal, and only i to 

 2 per cent, of acetic acid. The effect of distilling crude 

 cellulose, such as timber waste, is, however, very different. 



Cotton. Cotton grows chiefly in tropical and sub- 

 tropical regions, and requires a fair degree of moisture 

 and a moderately heavy soil. It grows as a small shrub, 

 and is planted at sufficient distances to allow hoeing and 

 picking by hand. In India two crops are sometimes obtained 

 in a year, but, as a rule, fallow or millets (Juari, bajra) or 

 pulses (gram) alternate. In the United States a three-course 

 rotation is adopted, with a resulting increase in the yield 

 of fibre. The plant yields a seed, to which the cotton 

 fibres adhere. Some varieties have only long fibres, which 

 are easily detached. Other varieties have, in addition, 

 small short fluff, which refuses to come off by any simple 

 process. Cotton fibre is a hollow, flattened, and twisted 

 tube in the better varieties (Sea Island), from about ij to 

 2 J inches long ; in the Egyptian kind the fibres are generally 

 from ij to 2j inches long, and in the Indian the fibres are 

 usually not more than about one inch in length, but in Indian 

 cotton considerable amounts of short fluff remain adhering 

 to the seed. Those varieties which produce a naked seed, 

 that is, a seed from which the long fibres are easily removed, 

 leaving the seed naked, are commonly called black seed. 

 Indian varieties, owing to the adhering fluff, are called white 

 seed. After the cotton fibre has been removed, the cotton 

 seed still has a considerable value, and is used as an oil 

 seed (see p. 137). Cotton flowers are used for dyes. The 

 cotton is bound with iron bands into bales, either circular 

 or rectangular. On arrival at the mills, the bales are broken 

 up and cleaned. The cotton fibre is then carded, passed 

 through a drawing machine, and finally made into thread. 

 It is then commonly woven into some kind of fabric for 

 the production of cotton cloth. Cotton is " mercerized," 



