426 



Further Observations on Cell-wall Structure as seen in Cotton 



Hairs. 



By W. Lawrence Balls, M.A., Sc.D. (Cantab.), and H. A. Hancock. 

 (Communicated by Dr. F. F. Blackman, F.R.S. Received March 3, 1922.) 



[Plate 10.] 



The present note summarises the results of observations made subsequently 

 to the recognition of growth rings in the cell-wall,* of which a photograph in 

 transverse section is given in Plate 10, fig. 2. These observations are all 

 related to previous physiological studies, and most of them have been made 

 on materia] of known origin, i.e., dated bollsf and pure-line plot crops. 



An excellent memoir on our present knowledge of the cotton cell-wall by 

 Mr. H. J. Denham,J now in course of publication, makes it unnecessary for 

 us to deal with the historical aspects of the matter. 



Methods. 



(a) The " swelling " technique has been further developed by the use of 

 calcium thiocyanate (for which, as well as for the use of naphthamine 

 blue as a stain, we are indebted to Mr. H. E. Williams§). Other reagents 

 have also been found serviceable when the conditions are adjusted to produce 

 an equilibrium state on the verge of actual solution, e.g., cuprammonium and 

 caustic soda, alone or together, and also sulphuric acid have been largely used. 

 The latter is exceptionally interesting as showing specific differences between 

 various hairs in respect of the critical concentration. The artifact nature of 

 swollen walls has been continuously borne in mind, and all observations have 

 been returned to the unswollen state by measurements of the contractions 

 and expansions experienced by the hair. 



(b) Our section-cutting technique has been described elsewhere.|| 



(c) The junior author devised a simple " pressure " technique, single hairs 



* W. L. B., " Existence of Daily Growth Rings in the Cell-wall of Cotton Hairs," 

 ' Roy. Soc. Proc.,' B, vol. 90 (1919). 



t W. L. B., "Raw cotton (Development and Properties of)," chapter 4 (London, 1915). 



X Denham, H. J., " The Structure of the Cotton Hair and its Botanical Aspects : 

 Memoir of the British Cotton Industry Research Association," ' Jour. Textile Inst.,' 

 vol. 13, p. 99 (1922). 



§ Williams, H. E., " The Action of Thiocyanates on Cellulose," ' Jour. Soc. Chemical 

 Industry,' vol. 40, p. 221 t (1921). 



|| Denham, H. J., 'Nature,' vol. 107, p. 299 (1921) ; W. L. B. and H. A. H, 1 Nature,' 

 vol. 107, p. 361 (1921). 



