I. The marine brown alga F. vesiculosus was re-examined for lipochrome pigments; whereas the living plant contains [beta]-carotene and fucoxanthin, the latter pigment is wholly replaced by zeaxanthin in the dead material. Fucoxanthin, carefully purified by chromatographic methods, has m.p. 166-168[degree] (uncorr.) and contrary to earlier statements is optically inactive.[long dash]II. The unsaponifiable material of various algae was examined and a relationship established between the algal spp. Whereas, in the Chlorophyceae, Ocdogonium resembles the land plants in containing only sitosterol, Cladophora sauteri and Nitella opaca contain both the former sterol and the algal sterol fucosterol; the latter alone is present in the marine alga Rhody-menia palmata. All the algae studied contained small amts. of hentriacontane and terpenoid material; a new phytosterolin, m.p. 283-285[degree], was isolated from N. opaca and Oedogonium. Whereas [beta]-carotene, lutein and tara-xanthin were isolated in all spp., [alpha]-carotene was observed in Oedogonium. The evidence adduced reveals that the Oedogoniales show a closer chemical relationship to the land plants than to the typical algae.[long dash]III. Lactoflavin, closely related to vitamin B2, which is widely distributed throughout the animal and vegetable kingdoms, was isolated from fresh- and salt-water algae as typified by Cladophora sauteri (flavin itself extracted) and F. vesiculosus (flavin as lumilactoflavin).