58 RELATION OF PHYLLQTAXIS TO MECHANICAL LAWS. 



by the parastichies are the only ones which give these intersections 

 alone, i.e., give the minimum of intersections. 



It remains to be considered why such numbers and ratios are 

 found, and to what extent the plant is restricted to such a series. 



Fig. 26. — Log. spiral construction for system (8 + 13) ; with curve setting of 

 preceding the genetic spiral winds left. 



Again, by using the same curve, and drawing eight long and 

 thirteen short spirals, a set of parastichies may be marked out which 

 will give equally correct results for the Pine cone (F. austriaca, 

 P. Pinea) ; and, on numbering the areas, they may be checked by the 

 actual specimen : all observed appearances are accurately imitated 

 in the diagram ; the axes of the rhombs of rhombs forming spirals 



