Write a note on Phaeophyceae.

(N/A) $\rightarrow$ The members of Phaeophyceae are commonly known as brown algae.
$\rightarrow$ Habitat: They are primarily found in marine habitats.
$\rightarrow$ Size and shape: They show great variation in size and form,ranging from simple branched,filamentous forms (e.g.,$Ectocarpus$) to profusely branched forms like Kelps,which may reach a height of $100 \ m$.
$\rightarrow$ Pigmentation: They possess chlorophyll $a, c$,carotenoids,and xanthophylls. Their color varies from olive green to various shades of brown depending upon the amount of the xanthophyll pigment,fucoxanthin,present in them.
$\rightarrow$ Stored food: Food is stored as complex carbohydrates,in the forms of laminarin or mannitol.
$\rightarrow$ Cell structure: The vegetative cells have a cellulosic wall,usually covered on the outside by a gelatinous coating of algin. The protoplast contains plastids,a centrally located vacuole,and a nucleus.
$\rightarrow$ Plant body: The plant body is usually attached to the substratum by a holdfast,and has a stalk,the stipe,and a leaf-like photosynthetic organ,the frond.
$\rightarrow$ Reproduction:
$\rightarrow$ Vegetative reproduction: Takes place by fragmentation.
$\rightarrow$ Asexual reproduction: In most brown algae,it occurs by biflagellate zoospores that are pear-shaped and have two unequal laterally attached flagella.
$\rightarrow$ Sexual reproduction: It may be isogamous,anisogamous,or oogamous.