Chapter VI 



EUPHYCOPHYTA 

 PHAEOPHYCEAE 



ectocarpales, sphacelariales, tilopteridales 

 cutleriales, dictyotales, chordariales, 

 sporochnales 



* General 



The algae composing this class range from minute discs to lOO 

 metres or more in length and are characterized by the presence of 

 the brown pigment, fucoxanthin, which masks the green chloro- 

 phyll that is also present. The class can be divided into a number of 

 orders and families, which can be treated independently (Fritsch, 

 1945)3 or the famiUes may be placed into three groups as proposed 

 by KyUn (1933). These groups are based upon the type of alterna- 

 tion of generations, though the classification involves difficulties 

 so far as one family (Cutleriaceae — see, however, p. 142) is 

 concerned. 



(a) Isogeneratae: 

 Plants with two morphologically similar but cytologically differ- 

 ent generations in the life cycle (e.g. Ectocarpaceae, Sphacel- 

 ariaceae, Dictyotaceae, Tilopteridaceae, Cutleriaceae). 



(^) Heterogeneratae: 

 Plants with two morphologically and cytologically dissimilar 

 generations in the life cycle : 



(i) Haplostichineae : Plants with branched threads, which are 

 often interwoven, and usually with trichothallic growth 

 (e.g. Chordariaceae, Mesogloiaceae, Elachistaceae, Sper- 

 matochnaceae, Sporochnaceae, Desmarestiaceae). 

 (ii) Polystichineae: Plants built up by intercalary growth into 

 a parenchymatous thallus (e.g. Punctariaceae, Dictyosi- 

 phonaceae, Laminariales). 



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