Write a note on Phaeophyceae. 

• The members of phaeophyceae are called brown algae.
• Habitat: Primarily found in marine habitats.
• Size and shape : They show great variation in size and form. They range from simple branched, filamentous forms (Ectocarpus).
• They are profusely branched forms as represented by Kelps, which may reach a height of 100 metres.
• Composition : They possess chlorophyll a, c carotenoids and xanthophylls. They vary in colour from olive green to various shades of brown depending upon the amount of the xanthophyll pigment, fucoxanthin present in them.
• Stored food : Food is stored as complex carbohydrates. The vegetative cells have a cellulosic wall usually covered on the outside by a gelatinous coating of algin.
• Form: In addition to plastids, a centrally located vacuole and nucleus is also present in cytoplasm.  
• The plant body is usually attached to the substratum by a holdfast, and has a stalk, the stipe and leaf like photosynthetic organ the frond.
  Reproduction :
•  Vegetative reproduction :
• Vegetative reproduction takes place by fragmentation
• Asexual reproduction : In most brown algae it is done by biflagellate zoospores that are pear-shaped and have unequal laterally attached flagella.
• Sexual reproduction : It may be isogamous, anisogamous or oogamous. Union of gametes may take place in water or with in the oogonium (oogamous species). e.g. Ectocarpus, Dictyota, Laminaria, Sargassum and Fucus are its common forms.