Porphyra umbilicalis, Kützing; Ulva umbilicalis, Eng. Bot. The fronds are delicately membranaceous, deeply and irregularly cleft into several broad segments. Their colour is deepish purple, but, when not in a state of perfection, it tends to livid olive. "Under the microscope, the whole frond appears to be divided into squares, in the manner of a tessellated pavement, and within each square are four purple granules or spores, which constitute the fructification and the whole colouring matter of the frond" [Harvey, Phycologia Britannica, vol. i. pi. xcii. 1846.] (see Fig. 154, a). Abundant on all our shores. This plant is pickled with salt, and sold in London as laver. The London shops are said to be supplied with it from the coast of Devonshire. When stewed, it is brought to the table and eaten with pepper, butter, or oil, and lemon juice or vinegar. Some persons stew it with leeks and onions. It is generally taken as a luxury; but it might be employed with advantage, by scrofulous subjects, as an alterative article of diet. In the absence of other vegetables, it might be valuable as an antiscorbutic to the crews of our whaling vessels cruising in high latitudes, where every marine rock at half-tide abundantly produces it.
The Elements of Materia Medica and Therapeutics, Vol. II, 3th American ed., was written by Jonathan Pereira in 1853.