194 



PHAEOPHYCEAE 



neighbouring cells, and in this manner proliferations are formed 

 which may also serve for vegetative propagation. Both crypto- 

 stomata and conceptacles arise as depressions in the surface of the 



Fig. 129. Fucus. A, adult plant of F. serratus ( x 0-30). B, a marsh form of 

 F. vesiculosus ( x 0-30). C-E, seedling stages of F. vesiculosus showing origin of 

 rhizoids and apical tuft of hairs. F, diagram to show method of segmentation of 

 apical cell, A. 6s = basal segment, 5S = side segments. G, apical cell of young 

 thallus. H, apical cell of old thallus. (A, B, after Taylor; C-H, after Oltmanns.) 



thallus and there are three principal accounts which have been 

 given of the course of their development : 



(i) An early view held by Kiitzing and Sachs in which they were 

 described as arising as slight depressions in the thallus that later 



