STRUCTURAL VARIATIONS IN HOMOLOGOUS CELLS 169 



Our present knowledge of cotton is in somewhat the same position. 

 We owe the relevant data to the careful determination by Meredith, at the 

 British Cotton Industries Research Association at Didsbury, Manches- 

 ter, of the refractive indices of large numbers of cotton fibres of various 

 lengths. The results, therefore, are quite comparable with those on the 

 outer layers in bamboo and show very similar phenomena. Again, 

 therefore, it is clear that, even in this peculiar type of cell with its 

 reversals of spiral sign, there is nevertheless the same kind of connection 

 between cell length and wall architecture. Certainly the spiral in cotton 

 is much flatter than we might have expected it to be in terms of the 

 enormous length of the cells, but this might easily be associated with 

 the reversals in sign. In fact, as far as the evidence goes at present, it 

 might be possible from the present point of view to consider cotton 

 hairs as a series of comparatively short cells arranged in a filament. 



Finally, brief mention may be made of monocotyledonous fibres, 

 other than bamboo, worked by Meeuse. Here we have available no 

 quantitative determinations at all, but Meeuse does make the remark 

 that there is a tendency for longer fibres to possess steeper wall spirals. 



Although quantitative relationships are therefore lacking except in 

 two cases, it seems at the moment very probable that the connection 

 between cell length and molecular architecture may be quite a general 

 one. The lack of a mathematical expression in three of the cases cited 

 here cannot be considered of much consequence, for the relationships 

 quoted for tracheids and bamboo fibres have no theoretical foundation 

 and must be regarded somewhat in the same way as are mathematical 

 expressions of growth rates, as convenient summaries of data with 

 no obvious fundamental significance. This is not to say, of course, 

 that the phenomenon itself is of no significance, just as it would 

 be nonsense to deny significance to the shape of a growth curve even 

 though the mathematical formulation of the curve has no fundamental 

 value. On the contrary, the connection between cell length and spiral 

 organization must reflect something very fundamental indeed in the 

 cell mechanism. What this something may be we can hardly hazard a 

 guess just now, and it is perhaps better to leave this chapter as a bare 

 record of the phenomenon. Indeed, we can hardly begin even to think 

 about the implications without paying first of all some considerable 

 attention to the conditions obtaining during the growth of the ceU. 

 It wiU therefore be as well to postpone any further discussion to the 

 end of the next chapter when we have before us the relevant information 

 concerning primary walls. 



