Brown algae (Phaeophyta).
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   Many brown algae are multicellular "seaweeds".
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   The sea palm lives along the Pacific coast of north America.
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   The thallus (undifferentiated tissue) is composed of
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<BR><LI> photosynthetic blades,
<BR><LI> a stipe that provides structural support, and
<LI> a holdfast anchors the organism to the sea floor.