rv. 



FUCACE^.— HiMANTHAXIA. 71 



7. Fucus vesicuhsus, Linn., frond flat, leathery, thick, linear, dichotomous, quite 

 entire at the margin, midribbed ; air-vessels globose or elliptical, mostly in pairs, 

 (often absent) ; receptacles terminal, turgid, ellipsoid, ovoid, or spindle-shaped. 

 /. Ag. Sp. Alg., vol 1, p. 210. Kiitz. Sp. Alg. p. 589- Turn. Hist. t. 88. E. 

 JBot. t. 1066. Harv. Phyc. Brit. t. 204. Fucus divaricatus, F. inflatus, F. spiralis, 

 F. volubilis, F. Slier ardi^ Auct. F. bicornis, and F. microphyllus, Be la Pylaie, ^x. 



Hab. On rocks and stones between tide-marks. Very common on all rocky 

 shores from Greenland to New York. Also on the N. W. coast ; in California, and 

 northward. (The southern limit on the east coast not ascertained.) (v. v.) 



Fronds from two inches to two feet long, or more ; varying from aline to nearly 

 an inch in breadth, flat, midribbed, many times forked ; often spirally twisted. 

 Air-vessels generally in pairs, one at each side of the midrib, spherical or oval, 

 their size varying with the breadth of the frond. Beceptades very turgid, and 

 filled with a lax, watery jelly, through which a network of delicate filaments 

 extends. Colour olive or brown. Substance coarse and thick. 



Very variable in size and degree of ramification, according to the locality in 

 which it grows. When destitute of air-vessels, it may be mistaken by the student 

 for F. ceranoides, but the frond is much thicker and more opaque than in that species, 

 and contains a far greater proportion of alkaline matter. The earlier writers on 

 marine plants made a great number of species out of this ; but its varieties only 

 appear different when isolated specimens are examined in the cabinet. On the sea 

 shore all the various forms may be seen passing into one another at difii'erent tidal 

 levels. F. vesicidosus is distributed in the northern Atlantic from the Arctic coasts 

 to the Canary Islands ; and in the Pacific, from Kamtschatka to California. It is 

 reported to have been brought from the Cape of Good Hope and from Australia, 

 but these localities want confirmation. On the east coast of America it and F. 

 nodosus constitute at least three fourths of the covering of tidal rocks. 



VI.— HIMANTHALIA. Lyngb. 



Boot a disc. Frond at first top-shaped, then cup-shaped, vesicular, unbranched. 

 Beceptades very long, strap-shaped, repeatedly forked, springing from the centre of 

 the cup-shaped frond, filled with mucus, traversed by jointed fibres, and pierced by 

 numerous pores, beneath which are placed the spherical conceptacles (or spore- 

 cavities). Spiore cavities diclinous. Sp)ores four within the same hyaline perispore, 

 several perispores attached to the walls of the cavity. Anther idia on branching 

 filaments, racemose. Paranemata simple, lining the cavity. 



