338 RELATION OF PHYLLOTAXIS TO MECHANICAL LAWS. 



Note IV. — Bulk-Batio. 



The bulk-ratio, defined as the ratio between the sectional 

 diameter of the lateral primordium and that of the axis at the 

 point at which the member was apparently inserted, was taken 

 as represented with approximate accuracy by the ratio of the 

 radius of a circle empirically described in a quasi-square mesh to 

 that of the circle drawn through the centre of the former 

 one (p. 88), and from such empirical constructions the angle 

 subtended by a primordium of any given system was approxi- 

 mately measured, well within any degree of observation error 

 on the plant. 



Since there can evidently be no ready comparison of bulk- 

 ratio between the circular section of an axis and the ovoid 

 section of a lateral member, this method will prove sufficiently 

 accurate. But it is possible to approach the subject from a 

 different standpoint. Thus, the angle subtended at the origin 

 by each ovoid primordium may be calculated mathematically, 

 and this angle may be compared with the empirical geometrical 

 construction. 



