Many are epiphytic on other algae, more especially the larger Phaeophyceae and Rhodophyceae.

In the case of marine algae, the hosts are chiefly the larger Phaeophyceae and Rhodophyceae.

Most algae, particularly Phaeophyceae and Rhodophyceae, spend the whole of the life-cycle immersed in water.

A census of Phaeophyceae is given below:-

A similar uncertainty exists with reference to certain groups of Phaeophyceae, and the matter will thus arise again.