124 TENTH ANNUAL REPORT OP 



Kelp is still made, on a small scale, for local consumption, and is 

 sometimes exported as manure, but at a very low price. It is not 

 likely ever to rise again into importance, except as a source of Iodine, 

 which singular substance was first discovered in a soap-ley made with 

 kelp ashes. Iodine has now become almost indispensable^ from its 

 medicinal value, as well as from its use in the arts and manufactures, 

 and has been found in greater quantity in the fronds of certain littoral 

 Alga) than in any other substances. It is therefore possible that, for 

 producing this substance, these kelp-weeds may again become of mer- 

 cantile importance. As a remedy in cases of glandular swellings^, the 

 use of Iodine is now well established, and it is a singular fact that 

 several littoral Fuci have been from early times considered popular 

 remedies in similar affections. Ficcus vesiculosus has long been used 

 by the hedge-doctors to reduce such swellings ; and Dr. Greville men- 

 tions, on the authority of the late Dr. Gillies', that the " stems of a 

 seaweed are sold in the shops, and chewed by the inhabitants of 

 South America, wherever goitre is prevalent, for the same purpose. 

 This remedy is termed by them Palo Goto, (literally, Goitre-stick,") 

 and Dr. Greville supposes, from the fragments which he had seen, 

 that it is a species of Laminaria. 



Iodine, however, though the most important, is not the only medi- 

 cinal substance obtained from the Algn3. GracUcma JielmintJiochorion, 

 or Corsican Moss, has long held a place in the pharmacoiioeia as a 

 vermifuge. What is sold under this name in the shops, is commonly 

 adulterated with many other kinds. In samples which I have seen, 

 the greater part consisted of Laurencia ohtusa, through which a few 

 threads of the true Corsican Moss were dispersed. Possibly, however^ 

 the Laurencia may be of equal value. 



31annUe also has been detected by Dr. Stenhousc in several Alg?e^ 

 to which it imparts a sweetish taste. The richest in this substance 

 appears to be Laminaria saccharina, from a thousand grains of which 

 121.5 grains, or 12.15 per cent., of mannite were obtained. The 

 method of extracting is very simple. The dried weed is repeatedly 

 digested with hot water, when it yields a mucilage of a brownish-red 

 color, and of a sweetish, but very disagreeable taste. When evapo- 

 rated to dryness, this mucilage leaves a saline semi-crystalline mass. 

 This being repeatedly treated with boiling alcohol, yields the mannite 

 in "large hard prisms, of a fine, silky lustre." Halidrys siliquosa, 

 Lo,mmaria digitata, Fucus serratus, Alaria esculenta, Bliodymenia 

 palmata, &c., are stated by Dr. Stenhouse, from whose memoir this 

 account is condensed, to contain from 1 to 5 or 6 per cent, of mannite. 



In summing up the economic uses to which Algas have been ap- 

 plied, I must not omit to mention their application in the arts. Tho 

 most valuable species, in this point of view, with which we are ac- 

 quainted, is the Gracilaria tenax of China, under which name prob- 

 ably more than one species may be confounded. Of this plant, on 

 the authority of Mr. Turner, (Hist. Fuc. vol. 2, p. 142,) " th^ 

 quantity annually imported at Canton is about 27,000 lbs., and it is 

 sold in that city at about 6d. or 8d. per lb. In preparing it, nothing 

 more is done than simply drying it in the sun ; after which it may 

 be preserved; like other Fuci, for any length of time, and improves 



