982 XIV. ALGiB. 



thought they could perceive in those Florideee which are parasitic on Chlorosporece is foreign to these 

 latter, as may easily be ascertained by transverse slices, which show two very distinct rings, the central 

 one green, the outer red. It is, however, certain that some Alga can only grow on the tissues of other 

 species, and some even only on a particular species ; as Elachista scutulata on Himanthalia, Ectncarpus 

 brachiatus on RJtodymenia palmata, Mhkophyllis dentataon Peyssonnelia Squamaria, Polysiphonia fastigiata 

 on Fuem nodosa, Sec, &c. Some Confervm and Saprolegniece develop on Fishes, which they finally 

 liill. The shell of some marine Tortoises of Japan are sometimes quite covered with Conferva, giving 

 them a most singular aspect. 



The marine Algse inhabit the most varied localities ; some affect the shore, others the open sea. 

 Everyone has heard of the immense bank of Seaweed {Sargassum nutans) floating in the middle of the 

 Atlantic Ocean, which Christopher Columbus crossed in 1492, in 38° 50', and again in 1493, in 37°, 

 between 40° and 43° W. long. Now, as this enormous bank of Sargassum still exists, we may conclude 

 that it has not changed its position during 350 years. The Polar seas support the largest Algte of the 

 groups of Phceosporeee, Laminarue, or Fucacea. Fueus vesiculosus grows on anything. The nature of the 

 rock on which they grow does not appear to be of importance to Algce ; the quality of the water, more or 

 less muddy, more or less tranquil, the exposure to the shock of the waves, the level of the beach, &c., 

 appear much more nece.ssary conditions for their development. On bottoms of pure mud scarcely any- 

 thing is found but Vaucheria, Diatomea, and some Osdllariece ; but on muddy rocks, and shores with 

 Zostera, the algological flora is often very rich, and contains a large number of peculiar species. 



The Alg(B of the open sea often live at very considerable depths : Udotea vitifolia has been brought 

 up from a depth of 250 feet, near the Canaries; P^ron and Maug6 have dredged up brilliant living 

 ^./;y<B from 560 feet; and Bory declares that he fished up iSar^flsswrn turlinatum from a depth of nearly 

 660 feet off the Isle of France.^ Anadyomene stdlata has been gathered at twenty fathoms in the Gulf of 

 Mexico ; Constantinia, at fifty fathoms in the Polar seas. Immense masses of Diatomece are met with 

 in the deepest abysses of ocean. Although, according to divers, light does not appear to penetrate 

 below fifteen fathoms, nevertheless the above-mentioned Udotea vitifolia was of a rich green colour, 

 comparable, according to Humboldt, with that of the leaves of the Vine and of Grass. The tempera- 

 ture suitable to the growth of Algts also presents remarkable differences. While Protococcus nivalis lives 

 on snow, and the largest Laminaria inhabit the polar regions, we meet with Algce also in thermal 

 springs : such as the Oseillariece, which in Tuscany inhabit boracic pools ; and Anabaina thermalis, which 

 grows in mineral waters of a temperature above 104° Fahr. 



As to the geographical distribution of Algce, Phceosporeee or Fucacecs prefer the cold regions of both 

 hemispheres ; nevertheless Sargassum abounds in tropical and subtropical regions. Rhodosporece or 

 Florideee principally inhabit temperate zones ; Chlorospm-ece or Confervce abound everywhere. 



The genera and species of Algce are infinitely less numerous than those of other Cryptogamic 

 families, but the number of individuals is much more considerable. The sounding lead brings them up 

 in masses from all depths, and Diatomece are at the present time aiding in the formation of siliceous 

 deposits similar to the fossil deposits which yield rotten-stone. Fresh- water Algce are much more abundant 

 than marine ; Confei-vce sometimes multiply enormously in winter in submerged meadows, and form a 

 sort of felt, which, on the retreat of the waters, remains dry, whitens, and is known by the name of 

 natural paper or water-flannel. 



The marine Algce which are medicinal agents owe their property as vermifuges to iodine, a powerful 

 medicine, and .to a very sweet volatile oil; as the Corsican Moss {Gigartina Ilelminthochorton) and the 

 comm.on Cotalline {Corallina o^cinalis). From the ashes of Wrack, iodine and soda are obtained. The 

 ashes of many species were employed as antiscrofulous and antiscorbutic before Courtois and Gay- 

 Lussac discovered and separated the simple substance iodine, now so much used in medicine. Ulva 

 Zactuea was formerly considered a resolvent and vulnerary ; Conferva rivularis, when distended with 

 water, is used as a topic for bmns. Several species contain a mucilage, which, when not altered by 

 iodine, renders them edible ; as in the Carrageen Moss (Chondrus polymorphus), which supports the poor 

 natives of the sea-shores of northern seas ; and as in Alaria escidenta, Phodymenia palmata [Dulse], Iflva 



' This I may venture to assure the reader is an exception of the Sargassum natans, which floats, in an 

 error ; Sargassa ara 6}B,inently littoral Algis, with the abnormal condition, in the Great Ocean. — Ed. 



