Height: Height of the thallus body may be up to a few metres.
Body Structure: Plant body can be divided into three parts:
i) At the lower pan of the body, there is a plate like compressed structure called holdfast
ii) Middle pan looks like a stem called stipe
iii) Upper branched leafy structure is called frond
1) Holdfast: It is plate like in structure. With the help of holdfast, the plant keeps its body fixed with any substratum such as, stone etc.
2) Stipe: It is the main basic structure of the plant
3) Primary and secondary branch: Many primary and secondary branches grow from the stipe which are more or less similar to leaf in structure, called primary branches.
Primary branch gives rise to secondary branches which are rod like in structure.
Few secondary branches are modified into air bladders which keep the plant body floating in water.
There are also some tertiary branches growing from the base of the air bladders which act as receptacles.
Habitat: They grow in warm sea of temperate region. Few species of them are found to grow in the coastal area of St Martin Island They are commonly known as Gulf weed.