LAMINARIALES (HETEROGENERATA^) i8i 



successive segment developing into a new lamina with its own 

 portion of stipe. Dried parts of the stipe, which can easily be taken 

 for pieces of driftwood, are used by natives to make knife handles. 

 This method of causing splitting should be compared with the 

 other processes found in Nereocystis^ Macrocystis and Postelsia 

 (cf. below). 



Lessoniaceae : Postelsia (after A. Postels). Fig. 122. 



This is a monotypic genus, often known as the "sea palm", that 

 is confined to the Pacific coast of North America where it grows 

 between Vancouver Island and central California on rocks which 



Fig. 122. Postelsia palmaeformis. (After Oltmanns.) 



are exposed to heavy surf. The smooth, glossy, cylindrical stipe is 

 thick but not very long, up to i m. in height. It is erect and hollow 

 within and bears at its apex a number of short, solid, dichoto- 

 mously branched structures from each of which hang 100-150 



