70 RELATION OF PHYLLOTAXIS TO MECHANICAL LAWS. 



metaphor, — in any Angiosperm apex, whatever its bulk and the 

 relative size of the primordia placed on it, the same system of 

 curved lines of equal action is normally utilized, and the con- 

 struction may thus be planned, within an extremely small range 

 of error, with the same log. spiral curves, for all but the lowest 

 terms of the series; further, any other parastichy ratio which 

 approaches 1 : 1-62 may be built up with the same curve, but 



Fig. 34. — Table sliowiiig direction of contact parastichies, and the genetic fiL^ 

 spiral/for successive systems of the Fibonacci series. ' -^ 



special curves must be drawn for a closer approximation to a 

 symmetrical pair. ; ' 



The theoretical interest of the table lies ir^ the fact, that if it is 

 the approximation of a certain ratio which is the essential point 

 in the scheme,' the appearance of other pa'rastichy numbers be- 

 comes conceivable so long as their ratio approximates 1 : 1-618. 

 That such is actually the case may be checked in the case of a 

 certain proportion of the inflorescence of DfpscMus and Helianthus. 

 The generalization of Wiesner, therefore, when applied more 

 legitimately to morphological relations without reference to 



