172 CHAPTER XI 



tive branches. Cottons with short-jointed fruiting branches are 

 more productive and usually earlier than those with fewer and 

 longer iuternodes." 



The seeds of cotton are borne in a leathery capsule, which 

 when mature is called a " boll." The " boll " may be sub- 

 globose, oval or ovate-acuminate. Three to four " locks " are 

 found in Sea Island and Egyptian types and four to five in 

 Upland kinds. 



Fibre. — There are generally two kinds of fibre on the 

 seed — (a) long hairs, lint or commercial fibre (staple), and (b) 

 short hairs or fuzz. The latter may be white, green or brown. 

 Some varieties produce no fuzz, and in these the seed is naked 

 when ginned. About one-third of seed cotton is lint. 



With regard to the fibre, Balls^ comments as follows : — 

 " The development of the fibre begins before fertilisation is 

 accomplished, by radial growth of a large number of the epi- 

 dermal cells of the seed coat. These cells differ in no respect 

 from their neighbours, and it seems possible that the density of 

 the coating may be determined by the external conditions dur- 

 ing a day or two after flowering. Possibly irregularity in 

 length may arise from distribution of the normal simultaneous 

 ' sprouting ' of these cells over several days. 



"The young fibre at once assumes its final diameter, which 

 is about twice that of the unaltered cell. It remains unicellular 

 throughout its career, and is always covered by the cuticle which 

 protected the original cell. The familiar heading which follows 

 treatment with ammonical copper hydroxide is simply due to 

 constriction of the swelling cellulose by the cuticular remains. 

 For the first day the nucleus lies at the tip of the swelling, but 

 after the third day it takes its place in the middle of the cell 

 axis, and there remains, either slung in cytoplasmic bridles or 

 at one side. The cytoplasm, of course, lines the whole cell 

 wall, and appears to remain alive until the boll cracks. 



" The growth of the fibre is at first confined to linear exten- 

 sion. In fact it seems that the boll attains almost to its full 

 size before any secondary thickening of the fibre wall begins. 

 By this time the fibre has reached to rather more than its final 

 ripe length. This period embraces about half the total matura- 

 tion period, being some 25 days. The final length is, of course, 

 constitutional, and can only be deflected from this constitutional 

 basis to a relatively slight extent. Even seeds which have not 

 been fertilised and consist of empty, undeveloped seed-coats 



