LAMINARIALES (HETEROGENERATAE) 179 



which the other developed, a speculation which is further supported 

 by the fact that S. dermatodea is more primitive because the stipe is 

 not twisted nor are the edges so wavy. The young sporophyte first 

 develops a juvenile blade which does not bear sporangia and then a 

 new and thicker basal fertile blade is intercalated, but it is only the 

 juvenile blade that bears the cryptostomata, thus suggesting that 

 these structures may be juvenile sexual conceptacles. 



Laminariaceae : Thalassiophyllum (thalassio, sea; phyllum, leaf). 

 Fig. 120. 



The perennial sporophyte is apparently composed of a spirally 

 twisted, fan-shaped lamina unrolling from a one-sided scroll 



Fig. 120. Thalassiophyllum clathrus. A-F, developmental stages to show the 

 origin of the single scroll ( x f ). G, adult plant. (After Setchell.) 



12-2 



