The  

members  

of  

phaeophyceae  

or  

brown  

algae  

are  

found  

primarily  

in

marine  

habitats.  

They  

show  

great  

variation  

in  

size  

and  

form.  

They

range   

from   

simple   

branched,   

filamentous   

forms   

(Ectocarpus)   

to

profusely  

branched  

forms  

as  

represented  

by  

kelps,  

which  

may  

reach  

a

height  

of  

100  

metres.  

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.  

Food  

is  

stored  

as  

complex  

carbohydrates,

which  

may  

be  

in  

the  

form  

of  

laminarin  

or  

mannitol.  

The  

vegetative  

cells

have  

a  

cellulosic  

wall  

usually  

covered  

on  

the  

outside  

by  

a  

gelatinous

coating  

of  

algin.  

The  

protoplast  

contains,  

in  

addition  

to  

plastids,  

a

centrally   

located   

vacuole   

and   

nucleus.   

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.   

Vegetative   

reproduction

takes   

place   

by   

fragmentation.  

Asexual   

reproduction   

in   

most   

brown

algae  

is  

by  

biflagellate  

zoospores  

that  

are  

pear-shaped  

and  

have  

two

unequal laterally attached flagella.