208 fl> o t e i s t a 



forms, while in others as the plants 

 increase in age the lamina becomes 

 characteristically wrinkled, ribbed or 

 furrowed. Such laminae are beautifully 

 displayed in Eisenia, Macrocystis and 

 Postelsia. 



Anatomically the kelps offer many 

 points of special interest. At a very 

 early age the epidermis is differentiated 

 from the cortical tissues within, and 

 almost as soon a distinction arises 

 between the pith and the area sur- 

 rounding it. Branches of the holdfast 

 are not provided with pith. This area 

 is similarly developed in stipe and 

 lamina. Anatomically the stipe and 

 lamina are fundamentally alike, thus 

 indicating that they should be taken to- 

 gether and considered in contradistinc- 

 tion to the holdfast. The principal 

 areas may be characterized briefly as 

 follows: The epidermis is composed of 



