Explanation:
Agar-Agar is obtained from the cell wall of red algae, mainly of the genus Gracilaria, Gelidium and Gigartina, etc. All of these algae are commonly characterized by belonging to the group of red algae because the predominance of the red pigment $r$ phycoerythrin in their body. These algae are small, have a reddish stem and are rich in mucilage, a type of fiber. These are extracted pouring hot water on them once they are dried in the sun.
