On Cell-wall Structure as seen in Cotton Hairs. 429 



and the short resembling slow spirals (fig, 4). However, as we have satisfied 

 ourselves that these spirals are not invariably opposed in direction, the fact 

 may not be relevant, though it does suggest a chemical polarity. 



These slow spirals are thus somewhat mysterious objects, and we must wait 

 for direct growth experiments to elucidate their nature. In passing, we may 

 note that the distortions produced by swelling make the quick pit spirals 

 simulate them very closely (fig. 8), a circumstance which led us to much 

 confusion at first. 



The Secondary Wall. 



One of us has formerly described the growth rings,* while many observers 

 have figured and commented on the existence of spiral markings in the wall 

 and on its inner surface especially. The occurrence of somewhat elusive 

 simple pits has also been described from fresh material by the senior author,f 

 and the probable existence of an internal spiral structure has been suggested 

 in various forms by non-botanical writers.* We are now in a position to 

 co-ordinate all these observations and views. 



By means of the simple " pressure " method, it is possible to " develop " a 

 spiral series of cracks throughout the length of a hair, with little distortion, 

 which can then be mapped in detail (fig. 6), and related to a previous charting 

 of the external form of the hair {vide infra). Such a pressed hair dissolves 

 much more quickly in swelling reagents, presumably from the greatly 

 increased free surface, and possibly also (since lower concentrations will 

 attack it), because the flank of the patterned and orientated cellulose 

 aggregates is, so to speak, exposed. When swollen, only a complex structure 

 resembling basket work is produced (fig. 5), and it was the spasmodic 

 occurrence of this in slides given us by Mr. Williams § which started the 

 present research. 



By mapping the simple pits in fresh greenhouse material, for which we are 

 indebted to Mr. Vernon Bellhouse, and then mapping their spiral cracks, we 

 have satisfied ourselves that the pits are simply abnormally wide intervals 

 between otherwise contiguous spirals. It is therefore possible that any plant 

 cell-wall which shows simple pitting may possess spiral structures similar to 

 that of the cotton hair. We would also call attention to the structures in 

 wood cell- walls described by Eobinson,[| who describes and figures these 



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

 * Roy. Soc. Proc.,' B, vol. 90. 



t W. L. B., " Eaw Cotton," fig. 12 and p. 78. 

 \ Vide Denham, Memoir, B.C.I. R.A., loc. cit. 

 § Williams, vide supra. 

 ]| Robinson, loc. cit. 



