TH^LLOGEX^. 725 



Distribution and Xumhers. — Algse ai'e more or less distributed 

 throughout the globe, gro-wing in salt or fresh water, or in moist 

 situations. Some species are found in 

 the boiling springs of Iceland, &:c. ; Fi^f. 1098. 



others occur in mineral springs, and 

 some in chemical solutions. The 

 waters of whatever temperature hare 

 their own peculiar forms. It is impos- 

 sible to estimate with any degree of 

 accuracy the number of species of 

 Algae, but they may be roughly guessed 

 at 2,500. 



Proj^ertiesund Uses. — Several species 

 are employed for food in diflferent parts 

 of the world; 2i»,Laminariasacehari?iG, Fia. lo*?. The Revoiv-ng 

 L. digitata L. j^ataioruni, #^ ; Aluria ^^S^J'^f^. 

 CL^Gulenta^ DurvuLcEa utilis, bargassum aied. 

 ^■pecies, IridcBa ediclis^ Chondnis crisjpus 



and C. marailhsus, Gdidiirm comeum, ^r., Gigartina spa-iosa, 

 Laurencia papulosa,, ^-c, Gracilaria UchcnoidiS and other Grc.cila- 

 rias, Ehodymcnia palrnata, Porphyra vvJgarls and P. laciniata, 

 Ulva latissima, U. compressa, S,-c. ; yostoc cdide, Hor mo siphon 

 arcticus ; and many others. The nutritious properties of the 

 above are due to the presence of starch, sugary matter {inanrdti'), 

 mucilage, and albumen. M. Payen has discovered a new principle 

 in GcUdium corneum (A^gt'.e de Jam), and some other Algse, to 

 which he has given the name of Geloae. To this substance also 

 tlie nutritious prop-erties of Algae are, to a great extent, due. 

 According to Payen, 1 part of gelcse dissolved in 500 parts of 

 boiling water, will afford, upon cooling, a colourless, transparent 

 jelly, — thus forming ten times more jelly than a like weight of 

 the best animal gelatine. In order, therefore, to produce a jelly 

 of equal consistence, it would be only necessary to employ the 

 tenth part of what is necessary when isinglass is used. Jellies 

 prepared from species of Gdidium, Lav.reneia, t^'c, are much 

 employed for food in China, Japan, &c. The edible birds' nests, 

 so highly valued for food, &c., in China, owe their properties 

 probably in part to certain species of Algae, but essentially to 

 the secretions of the swallows by which they are constructed. 



In medicine the above-mentioned nutritious Algae may be used 

 for their emollient and demulcent properties. Several species of 

 Algae, particularly Ficcus vcsiculosus, have been also employed 

 as remedies in G-oitre and scrofulous diseases. They owe their 

 beneficial effects in such cases, principally, to the presence of a 

 small quantity of iodine. The ashes obtained by burning many 

 species of Algse in the open air form the substance called ke'p, 

 which was formerly much used for the preparation of carbonate 

 of soda; but this is now more cheaplv oltained from sea-salt. 



