They have thalloids with chlorophyll. In this there is no embryo stage and non jacketed gametangia are present. In the previous classifications algae were placed in plant kingdom. While in five kingdom classification algae are groped in monera, protista and plantae. Their structure varies from filament shapes to large sheets. Their length is more than 50m. The filaments are attached by holdfast. Algae are covered by mucin. It protects the algae from excessive growth and drying conditions. They have no vascular and mechanical tissue. Their body is flexible and can bear the turn and tides of ocean. They are present in the water so they do not require water conduction. They have photosynthetic mode of nutrition with presence of chloroplasts. They have chlorophyll a, carotene and xanthophylls. They mainly reproduce by vegetative and asexual reproduction. Mitospores and meiospores are the main asexual spores. Sex organs are without any jackets. Sexual reproduction occurs by isogamy, anisogamy and oogamy. It occurs near the end of growing season. They have no embryo stage and life cycle can be haplontic or diplontic type.