1971. Pigments, polysaccharides, and photosynthetic products of Phaeosaccion colli~rsii. Can. J. Bot. 49: 1067-1074. Zoospores of Phaeosaccion collinsii averaged 70 p3 and contained total N 2.24 pg, DNA 0.19, and chlorophyll a 0.62 pg per spore. In addition, chl c, "cis"-8-carotene, fucoxanthin, and violaxanthin were principal pigments and a minor unidentified carotene was present.Photosynthetic rates of zoospores were 0.37 X 10-l2g C per spore per hour, or 0.59 mg C per mg chl a per hour at 5". The principal products of photosynthesis were mamitol and a water-soluble glucan.Carbohydrates in the thalli were fractionated and evidence is presented for the presence of a laminarinlike glucan, mamitol, tnyo-and scyllo-inositols. Alginate was absent.The relationship of P. colli~uii to other algal groups is discussed and it is concluded that its affinities lie with the Chrysophyceae.