Abstract
Monthly samples of the common British Laminariaceae and Fucaceae taken during 1946 have been analysed for cellulose.The cellulose content has been found to increase with the depth of immersion of the weed.In the Laminariaceae, both in the stipe and frond it undergoes marked seasonal variation, exhibiting two maxima, March/April and September/October with a distinct minimum in June/July.In Laminaria cloustoni, in March, maxima of 5·7 (dry basis) occur in the fronds and 10·3% in the stipes with minima, in June, of 4·1 and 8·4% respectively. In Laminaria saccharina the cellulose content (dry basis) varies between 4–5% in the frond and 7–8% in the stipe and in Laminaria digitata between 3–5% in the frond and 6–8% in the stipe.