548 Dr. W. L. Balls. The Existence of Daily 



of the process. The results were in no way peculiar on the cytological side, 

 the hairs being simple cells with a large single nucleus and persistent cuticle, 

 which grow to their full length during the first half of the maturation period 

 of the fruit, and lay down secondary deposits of cellulose on their primary 

 cuticularised wall during the latter half of the maturation period. For the 

 purpose of these studies a large number of open flowers of my pure strain 

 No. 77 were labelled on July 9, 1913, at the Giza Cotton Experiment Station, 

 and a few were collected and pickled every three days until the fruits opened 

 around the 50th day ; a single boll from several stages was available for the 

 present observations, of which the following are representative. 



Nine-day Fruit. — The lint and fuzz are scarcely altered by the hydration 

 process, and it is debatable whether any swelling of the wall has taken place 

 at all. Judging by the proximity of the protoplasm to the cuticle at points 

 where a hair had been accidentally bent, this swelling, if any, does not 

 increase the wall thickness to more than 8 per cent, of the cell diameter, 

 under parallel treatment with the well-swollen later fruits. Judging by the 

 slight increase in visibility of the cuticle, such swelling may have happened, 

 and this is supported by indications of wrinkling of the cuticle in surface view. 



The primary cell wall can only contain a relatively small amount of 

 cellulose, and probably the cuticle constitutes not less than one-third of its 

 weight. 



Twenty-07ie-day Fruit (fig. 2). — In spite of the great increase in lint length, 

 which now approaches its adult value, the same description applies as for the 

 nine- day specimen, with the exception of perhaps one hair in every few 

 hundred, which is slightly swollen, so that the cell diameter is increased by 

 about 30 per cent. 



Twenty-seven-day Fruit (fig. 3). — Previous work had shown that the 

 secondary thickening, with its concurrent formation of simple pits in the 

 wall,* and the consequent ability of the hair to twist on drying, began round 

 about the 21st-25th day. 



Conformably with this we find that these hairs, under the xanthate treat- 

 ment, present the typical beaded appearance. The great majority are 

 swollen to three or four times the cell diameter, and the wall thickness in 

 the swollen state may be equal to the cell diameter of the untreated hair. 

 The remains of the cuticle, torn by this swelling but not themselves swollen, 

 assume the position of girdles of various widths, or of spiral bands ; both 

 these formations are familiar as the result of treatment with cuprammonium 

 solvent.! 



* * The Cotton Plant in Egypt,' p. 84, and ' Raw Cotton,' pp. 74, 77. 

 t O'Neill, C, ' Calico Printing and Dyeing,' London, 1862, and others. 



