40 RELATION OF PHYLLOTAXIS TO MECHANICAL LAWS. 



thus five-sided cells are produced at the ends of the segments, which 

 on further orthogonal division render the system quite irregular 

 (fig. 18; 8, 9). 



Spiral-vortex construction is thus almost entirely masked by 

 secondary phenomena due to — 



(1) The shape of the iaitial cell. 



Fig. 17. — Hypothetical log. spiral construction for 3 series of segments at an apex ; 

 construction for 3-sided cells by circles, intersecting at 120° and 90°. 



(2) The effect of the individual growth of the lateral members. 



(3) The effects of tensions produced by fused lateral contact. 

 The effect of dividing up the initial cell into several initials 



segmenting contemporaneously would be to render the symmetry 

 circular, and the formation of such a system of cell-division pro- 

 ceeding from a single initial in a tissue-mass, in which circular 



