CHAPTER XVIII 

 LIFE HISTORIES OF ALG^ (CONCLUDED) 

 DICTYOTA DICHOTOMA 



227. Habitat. — ^Like Ascophyllum and Fucus, Dictyota 

 dichotoma grows chiefly along the ocean margins in the 

 zone between the lines of high and low tide. It is thus 

 subjected to alternate wetting and drying, and to rhyth- 

 mically alternating changes of light and temperature. It 



Fig. 177. — Dictyota dichotoma. Left, sporogonial plant; right sperma- 

 gonial (gametophytic) plant. (After W. D. Hoyt.) 



is found from as far north as the middle of the Scandi- 

 navian peninsula to about 40° south latitude. 



228. Description.— The plant body (Fig. 177) is a 

 thallus, flat, and branching profusely by forking at the 



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