1911 Encyclopædia Britannica/Algae/Uses
Algae cannot be regarded as directly important in the industries. On the coasts of Europe marine algae detached by Uses. the autumnal gales are commonly carted on to the land as a convenient manure. Porphyra laciniata and Rhodymenia palmata are locally used as food, the latter being known as dulse. Agar-agar is a gelatinous substance derived from an eastern species of Gracilaria. The ash of seaweeds, known in Scotland as kelp, and in Brittany as varec, was formerly used as a source of iodine to a greater extent than is at present the case.