142 THE DEVELOPMENT OF KAW COTTON 



wall to affect the strength somewhat ; but just as 

 flowering is the main determinant of yield wall thick- 

 ness must be the main determinant of hair strength, 

 while texture can only affect it secondarily as to strength, 

 though possibly greatly in regard to lustre. We have 

 also seen that hair strength is a definitely inherited 

 peculiarity, though subject to much greater fluctuation 

 than length, some strains never making a very thick wall, 

 while others make very thick ones whenever they are 

 given an opportunity. 



A side-issue of great importance from this discussion 

 of hair strength relates to the diameter of the fibre. 



This we have seen to be comparatively 

 Diameter. .... 



constant within a pure strain; but since 



there is a little uncertainty in some previous writings on 

 this subject, it may be well to discuss the matter more 

 fully. The diameter of the developing hair cell is fully 

 attained almost immediately, though the position of the 

 maximum diameter in the full-grown lint hair may vary 

 with different kinds of cotton, and cannot be settled till 

 the hair has grown to its full length. 



This diameter is that of a very thin- walled and more or 

 less cylindrical tube. The diameter of the ripe lint hair 



Diameter * s ( l u ^ te different : the walls of the tube have 



affected been thickened, and then have collapsed 



by Hair (Fig. H). Obviously, if the thickening has 



been negligible, the width of the ribbon t JLUS 



formed will be one-half the circumference of the original 



tube. If, on the other hand, thickening has been so 



complete that the tube becomes a solid rod, it will not 



