Focus vesiculosus- brown algae, natural source of iodine, collidal extracts with industrial uses similar to agar, common on rocky seacoasts, have a life span of four years, air bladders are frequently present and these help to keep the plant afloat when submerged, brown algae undergo a complex life cycle involving alternation of generations
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http://www.britannica.com/bcom/eb/article/3/0,5716,36223+1+35557,00.html
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