432 Dr. W. L. Balls and Mr. H. A. Hancock. 



in length to determine the causation of such abnormalities in it as we have 

 mentioned. Physiological work in this direction, under glass, is contemplated. 

 But this leaves unsolved the more fundamental problem, as to why even the 

 primary wall should be thus patterned and heterogeneous, consisting of 

 structures which can sometimes be mechanically broken apart, which are 

 possibly only united by a molecular film of water, and which show (when 

 enormously swollen and stained with naphthamine blue) granular lines 

 alternating with clear zones (fig. 8). 



Until a late stage we were not certain whether the slow spirals were not 

 always opposed in direction of rotation to the pit spirals, and a working 

 hypothesis was adopted which combined Church's results* on the fundamental 

 geometric structure of the cell with a general idea of protoplasmic circula- 

 tion, and with some earlier studies of growth in a fungus hypha by one of us.f 

 This hypothesis, though now entirely speculative, may yet be of interest. It 

 postulated the existence of two " growth centres " mutually exclusive or 

 polar in their inter-relations, as a rule ; these controlled the longitudinal 

 extension of the cell by intussusception, and their micro-bio-chemical opera- 

 tions were rhythmic, as in Liesegang ring-formation. It was unlikely that 

 such a system would build forward along a straight line, hence revolution 

 was postulated, sometimes right-handed, sometimes left-handed (fig. 3), under 

 the influence of accident or environment or even of stereo-isomerism. This 

 revolution of the builders produced the spiral form, their rhythmic operation 

 the successive fibril phases ; and molecular predetermination, akin to crystal- 

 lisation, produced fibrillar continuity. 



When it became clear that the slow spirals were not the trails of these 

 " growth centres " — since their direction was not invariably opposed to that 

 of the pit spirals — the hypothesis became mere speculation. 



It does, however, remain clear that there is a fundamental geometric 

 structure in the cell wall, though our hope of confirming and extending 

 Church's main conclusion has at present failed. 



The Protoplasmic Debris. 

 We have only to mention that this is of assistance in swelling technique as 

 a rough guide to the amount of longitudinal contraction. 



The Convolutions. 



We now come to a much observed feature of the cotton hair, about which 

 nothing definite has been published, whether in respect of their effect on 

 * Church, A. H., " Phyllotaxis in Eelation to Mechanical Laws " (Oxford University 

 Press, 1904). 



t W. L. B., " Temperature and Growth,'' 'Ann. Bot.,' 1909. 



