6o Sarah M. Baker 
-§ h - s FUCUS VESICULOSUS 
■&— “ ASCOPHY LLUM NODOSUM 
» FUCUS SPIRALIS 
Fig. 1. Diagram illustrating the variation in the nnmber of gametes 
expelled, with time of exposure. The arrows indicate the points at which 
the dehiscence mechanism of each species may be considered to have become 
efficient. The dotted curve represents the proportional values found for 
Fuats spiralis by weighing the gametes. 
