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A TEXTBOOK OF THEORETICAL BOTANY 



medullary filaments. In Fiicus we have an example of an Alga which grows 

 only at the tips of the fronds. The cells cut off from the apical cell form at 







t'lG. 125. — Fucus 7'esiculosus. Plant showing 

 air bladders. Much reduced. 



first a close tissue, but lower down the central ones elongate into filaments, 

 while the superficial layers remain parenchymatous. 



Fig. 126. — Funis serratus. Plant showing toothed 

 margins, and fertile regions at end of branches. 

 Much reduced. 



Because it possesses an apical cell the thallus structure of Fucus is usually 

 placed in contrast with the filamentous and trichothallic growth of lower types 

 like Ectocarpus and Cutleria, but in reality it is based upon a filamentous plan. 



