ALGAE

Nearly all of the Algae which are of any economic importance are included in the marine forms collectively known asseaweeds. Ofthe four principal groups only two, namely, the brown algse (Phseophyceae) and red algse (Rhodophycese), yield commercial products. On account of their large yield of mucilage quite a number are used locallyforfoodpurposes. The ash of a number of the kelps, as Fucus, Laminaria, etc., still continue to be the source of iodin. A few of the kelps have been used in phthisis, their value no doubt being due to the iodin content.

LAMINARIA. Devil's Apron. The cylindrical stipes and basal portions of the midribs of the fronds of Laminaria digitata and L. clustoni (Fam.Laminariaceae). The for merisavery characteristic kelp which is common north of Cape Cod. The fronds are attached to the rocks by fibers which are frequently arranged in whorls and from which arise a stout and solid stipe, from 3 to 15 dm. in length and which is more or less cylindrical below, compressed above and free from distinct mucilaginous cavities (muciparous glands). When well developed the stipe projects rigidly above the surface of the water at low tide and from which extends the oval or lanceolate lamina, which at the summit is split into digitate segments varying from 6 to 18dm. In leng than d 3 to 9dm. In width. L. clustoniisa common European form and resembles L. digitata. In the preparation of the commercial article the stipes and lower portion of the midribs are cut into pieces of convenient length and quickly dried. They were formerly used in the manufacture of tents and bougies, to which they were well adapted, owing to the fact that the cell walls are mucilaginous, so that the stipes increase six-fold upon the absorption of water from the parts to which they may be applied. As they cannot be sterilized without losing this property, they have been replaced by other materials. In a similar way a number of other vegetable substances have been used.

Description. In more or less cylindrical or slightly flattened or bent pieces of variable length and 10 to 20 mm. in thickness; externally, grayish-brown or dark brown, longitudinally furrowed and wrinkled; fracture tough, horny; internally, dark brown having a slight saline odor and a mucilaginous, slightly saline and bitter taste.

Inner Structure. The stipes show two well-differentiatedlayers, an outer one of narrow cells with brownish walls, and a middle portion consisting of very long hypha like cells, with thick, porous, mucilaginous walls. The cells contain numerous brown chromatophores, the brown pigment of which is soluble in water, leaving the green chloroplasts unaffected.

Constituents. About 47 per cent of mucilage; tangic acid 19 per cent; cellulose 11 per cent; ash 13 per cent, of which two-thirds is soluble in water; iodin from 0.06 to 0.11 per cent. The iodin is apparently combined in an organic form and is soluble in water, alcohol, acetone, alkalies and acids. Tunmann was able by means of very clever technique to detect microchemically the presence of iodin in 0.001 to 0.002 gm. of Laminaria. Sections of the fronds were placed in conjunction with starch upon slides and strong nitric acid added, the liberated iodin unites with some of the starch grains, staining them a blue color.

Literature. Tschirch, Handbuch der Pharmakognosie.

Soure: Scientific and applied pharmagognosy by Henry Kraemer, New York, John Wiley & Sons, Inc. London: Chapman & Hall, Limited 1920