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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