256- ALG^ 



cover a larger amount of surface of tidal rocks than all the other sea- 

 weeds together. Among these may be especially mentioned the familiar 

 bladder-wrack, Fucus vesiculosus, so abundant on all our coasts. The 

 well-known gulfweed, Sargassum bacciferum, distinguished by its berry- 

 like air-bladders, a native of warmer seas, is sometimes thrown up 

 on our shores, where it is carried by the gulf-stream. It very rarely 

 fructifies ; detached pieces, buoyed up by the air-bladders, being able 

 to retain their vitality for an indefinite length of time. An enormous 

 floating mass of this seaweed, consisting entirely of detached pieces, 

 is said to cover an area of 2oo,t30o square miles in the Atlantic, 

 about lat. 20-25° N. and long. 40° W., where it has maintained itself 

 with but little shifting since the time of Columbus, affording a home 

 and breeding-place for countless numbers of marine animals. The 

 family is, however, chiefly European ; a large proportion of the species 

 live only in shallow water, being exposed at every ebb-tide, or only 

 at neap-tides, when fertilisation takes place. The distinctions be- 

 tween the different genera are made to rest on the disposition of the 

 air-bladders and conceptacles, and on the more or less distinct differen- 

 tiation of the leaf-like organs. The frond of Splachnidium is partially 

 gelatinous. The structure of that of Durvillsea, one of the largest of 

 seaweeds, is very beautiful, being permeated by very large and regular 

 cavities resembling a honeycomb. Together with the Laminariacese, our 

 native Fucacese are largely used in the manufacture of kelp, though not 

 to the same extent as formerly, and as a source of iodine ; they are also 

 employed by farmers as a manure for their fields; On the coast of 

 Chili the poorer classes use a species of Durvillaea for food, and a soup 

 is made from it which is mucilaginous and sweet. 



Literature. 

 Agardh — Species, Genera, et Ordines Fucoidearum, 1848. 

 Thuret— Ann. Sc. Nat., 1854, p. 195. 

 Pringsheim — Monber. Berlin. Akad. Wiss., 1855, p. 133. 

 Rosanoff— (Pigment) Mem. Soc. Sc. Nat. Cherbourg, 1867, p. 145. 

 Millardet — (Pigment) Comptes Rendus, Ixviii., 1869, p. 462. 

 Kraus et Millardet — (Pigment) Mem. Soc. Sc. Nat. Cherbourg, 1870, p. 23. 

 Kny — Bot. Zeit., 1872, p. 699; and 1875, p. 450. 

 Sorby— (Pigment) Proc. Roy. Soc, 1873, pp. 455 et se(i. 

 Reinke— Jahrb. wiss. Bqt., 1876, p. 399 ; and Bbt. Zeit., 1877, p. 651. 

 Roslafinski — Beitr. z. Kenntniss d. Tange, 1876. 

 Thuret & Bornet — Etudes phycologiques, 1878. 

 Kuntze — (Sargassum) Engler's Bot. Jahrbuch, 1880, p. 191. 

 Bower — (Conceptacle) Quart. Joum. Microsc. Sc, 1880, p. 36. 

 Berthold — Die Cystoseiren (Fauna u. Flora Golfes Neapel), 1883. 

 Hanstein — Sitzber. Phys.-Med. Gesell. Wiirzburg, 1884, p. 104 ; and Arbeit. Bot. 

 Inst. Wiirzburg, 1885, p. 289. 



