PVCAl 19 



lower, sometimes more than two inches broad, and remark- 

 ably rounded, qoI unlike the webbed feel of some water- 

 fowl; and in Greville's variety laciniatus the Berratures 

 are very deeply cut, "and cleft or laciniate." 



13. nodosus [The knobbed Fueus ; frond compressed, without 

 distincl ril>,l lathery, Bubdichotomous ; branches Btrap-shaped, 

 Bomewhal pinnated, attenuate at base, remotely toothed, here 

 and there Bwelling into oblong air-vessels ; receptacles lateral, 

 orate, Btalked, springing from the axils of the marginal teeth, 

 Linn. Sp. PI. p. L628. Ltlas, PL IV. Fig L3 

 Halidrys nodosa, Lyngb. Physocaulon nodosum, Kiiiz. Ozo- 



thallia vulgaris, Dne. 

 Hab. Growing on submarine rocks and large boulder stones, 

 from ordinary high- water mark to half-tide level. Perennial. 

 Winter and spring. Very common. 

 This is the largest of the British Bpecies of the restricted 

 genus Fucus, and by far the toughest and most rigid. Its 

 Bubstance is thicker and denser than that of any of the 

 others, and its frequently pinnated habit, and remarkably 

 large vesicles, added to the ribless frond, afford Btrong 

 marks of distinction. When in fructification, the great 

 abundance of the clear yellow receptacles contrasts agree- 

 ably with the colour r.i' the other parts of the frond. Like 

 most other submersed plants, this varies in luxuriance ac- 

 cording to the depth at which it gTOWS : specimens near 

 high-water mark being short ami bushy, often exceedingly 

 crowded in branches, and thickly covered with fruit ; while 

 those produced near ordinary low-water are drawn out to 

 a great length, with more distant branches. 



11. IVIackaii (MacJcay's Fuous ; frond cylindrical or Bubcom- 

 pressed, Blender, much branched; branches dichotomous; 

 air-vessels elliptical, solitary ; receptacles Lateral, Lanceolate, 

 ovate, or forked, stalked, pendulous, scattered, near the base 

 of the branches, Turn. Hist. t. 52. (Atlas, PI. W 

 Fucus nodosus, y. Mackaii, Ag. Physocaulon Mackaii, Ktitz. 

 Hab. > usually in Land-locked bays, and among boul- 



ders. Perennial. April and Maj . 



is Mackaii was discovered in the year L806, on the 



in coast of i reland, by \h\ dames To* usend Mackay, 



author of the ' Flora Hibernica,' in honour of whom the 



3 has been named by .Mr. Haw son Turner in his 

 work, the ' Historia Fucorum.' For a Long time the fruc- 

 tification remained undiscovered, and, consequently, a doubt 



