The basal cell of $Ulothrix$ is known as:

Brown algae is characterised by the presence of

Seaweeds are an important source of

Which of the following statements are applicable to brown algae?
$(I)$ They contain pigments like chlorophyll $a$,chlorophyll $c$,carotenoids,and xanthophylls.
$(II)$ They vary in color from olive green to various shades of brown.
$(III)$ Food is stored as complex carbohydrates,in the form of laminarin or mannitol.
$(IV)$ The cell wall is composed of cellulose and algin.
$(V)$ The cell wall is covered on the outside by a gelatinous coating of algin.

In Thallophyta,sexual reproduction occurs by:

Agar-agar is obtained from