182 RELATION OF PHYLLOTAXIS TO MECHANICAL LAWS. 



with terminal capitulum 100 mm. by 50 mm. ia diameter, and ten 

 lateral branches fertile, and thirty-five lateral capitula well devdoped, 

 gave : — 



The plant was thus remarkably constant throughout to the bijugate con- 

 struction ; in a few capitula, as counted at the broadest diameter, slight 

 irregularities occurred, but only four tertiary heads suggested a reversion 

 to normal (21 + 34). As previously noted, the difference between the 

 prominent sets of curves is due to the fact that the florets which are here 

 counted do not necessarily present the same contact-relations as the 

 primary leaf-members which subtend them. 



(3.) Dvgsacus fullonum, a strong plant grown in the open, 5 feet high ; the 

 terminal capitulum perfectly cylindrical and 100 mm. long by 40 mm. in 

 diameter, exhibited the type 16, 26, 42, unchanged throughout almost the 

 entire length of the capitidum : 14 lateral capitula gave : — 



