Gelidium corneum.

Botanical name: 

Gelidium corneum Lam. Algae. Kanteen.

This seaweed occurs almost everywhere. In Japan, kanteen, or vegetable isinglass, is prepared from it, which is eaten. The cleansed plant is boiled in water, the solution is strained and allowed to set to a jelly in wooden boxes. The jelly is cut into long prisms, frozen and then allowed to thaw in the sun. The water runs away as the thawing proceeds, leaving a white skeleton of kanteen. One part will make a firm jelly with 150 parts of water.

Sturtevant's Edible Plants of the World, 1919, was edited by U. P. Hedrick.