CHAPTER XI 

 PHYLUM V. PHAEOPHYCEAE 



THE BROWN ALGAE 



301. The Brown Algae which are almost wholly marine 

 plants of shallow waters, numbering about 1000 species, 

 are all truly cellular, and range from small filamentous 

 few celled plants, to large massive organisms differenti- 

 ated into roots, stems and leaves. They are brown- 

 green in color, and contain other coloring matters in their 

 cells in addition to chlorophyll. They are propagated 

 mostly by laterally biciliated zoospores, and generated 

 in the lower families by isogametes, and in the higher 

 families by heterogametes, their union in all cases pro- 

 ducing a simple zygote. The gradations in the sexual 

 union of the gametes include (1) biciliated isogametes, 

 (2) biciliated heterogametes, (3) biciliated (or uniciliated) 

 sperms and non-ciliated eggs. 



302. In this phylum the dominant feature is the addi- 

 tion of the brown pigment, phycophaein, to the chloro- 

 phyll of the cells. With this character must be associated 

 the typically motile, usually biciliated gametes, produc- 

 ing simple zygotes upon uniting, and the rooted plant 

 body (from filamentous and small, to massive and 

 large.) 



303. Brown Algae probably originated in the vicinity 

 of Ulotrichaceae in the Chlorophyceae. The phylum 

 constitutes a "side line" diverging from the main evolu- 

 tionary stem or current. 



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