148 THE DEVELOPMENT OF RAW COTTON 



dying cell. This brings the whole question of these varia- 

 tions in the convolutions of lint hairs into line with other 

 botanical investigations on pits in cell walls, and, although 

 there are practically no data of the kind we require which 

 are available at the moment, we shall be able to utilize 

 them when they are obtained with other plants. The 

 ideal cotton sample is one in which all the hairs are of 

 the same length, diameter, and wall thickness, while all 

 have the same number of convolutions per fibre in the 

 same direction, spaced at equal intervals from end to 

 end. Such a sample would interlock in spinning so as to 

 give the maximum resistance to slip for whatever twist 

 it received. 



In the first place, the convolutions of the fibre do not 



always run in the same direction, but the direction 



reverses at intervals. It is not easy to say 



whether this is an advantage or not, under 

 Convolutions. 



present conditions of spinning, for it should 

 be remembered that, if all fibres were similarly convo- 

 luted, they would always have to be spun with the same 

 direction of twist, if the maximum strength were desired. 

 As to the causes of this reversal in twist, we can only con- 

 jecture that they result from some check in growth, 

 taking place about the thirtieth day of boll develop- 

 ment, when the secondary thickening is beginning, lead- 

 ing to irregular differentiation of the pit areas on the wall. 

 They cannot be determined later than this, since other- 

 wise the pits would not be formed through the whole 

 thickness of the wall. They might possibly be determined 

 earlier. 



