354 FUCUS DISTICHUS AS AN IRISH PLANT. 
nates, it is always broadest below, and tapers gradually in a slender 
acuminate barren apex. 
In size and habit F’ distichis is not unlike F. canaliculatus, Linn. 
but it belongs to the restricted genus Fucus, which is separated from 
Fucodium by the presence of a midrib; it has in this respect closer 
affinities with F. vesiculosus, Linn., and F. Ceranoides, Linn., but its 
size and habit, at least in the British specimens, are very different. 
Fucus distichus, Linn, Stipes short, cylindrical. Frond repeatedly 
dichotomous, linear, without air-vessels, flat and costate below, 
terete above; margin entire. Receptacles terminal, lanceolate- 
acuminate, slightly compressed, generally in pairs. 
F. distichus, Zinn. Syst. Nat. ii. p. 716; Turner, Fuci, i. p. 1. t. 45 
Lyngbye, Tent. Hydro. Dan. p. 6.t.1,C; J. Ag. Sp. Alg. i. p- 209; 
Harvey, Nereis Bor. Amer. p. 69. 
F. linearis, Z7. Dan. t. 351 (excl. syn. Huds.). 
F. filiformis, Gmel. Hist. Puc. p. 12. t. 1 A. f. 1. 
F. furcatus, ante, p. 283. 
Has. On the perpendicular western face of Duggerna rock, Kilkee, 
Ireland (Harvey and N. B. Ward! ; 
Groe. Dist. Atlantic shores of Europe, Greenland, and Newfound- 
land. 
Root a conical expansion, a quarter of an inch or more in diameter. 
Stipes in the Frish specimens short and cylindrical. Frond somewhat 
smaller than in foreign specimens, two to four inches long, repeatedly di- 
chotomously forked, flat, aud when fresh, with a distinct midrib or longi- 
tudinal thickening, and a narrow web on either side in the older portions 
of the plant ; the younger branches are nearly cylindrical, and the bansa 
summits are blunt; the margin is very entire. The frond is without 
air-vessels, but has scattered over its surface a number of minute pores, 
om which issue several short simple filaments composed of about four 
elongated cells. Receptacle generally terminal in pairs, lanceolate-2cu- 
minate, considerably wider than the segments, which support it, broadest 
at the base, gradually narrowing upwards, and terminating in a pro- — 
duced acuminate barren point. Sometimes only one of the forked 
branches bears a receptacle, the other continuing to grow, and branch. 
Some plants present also a receptacle, which is occasionally lateral, on 
the older portions of the stem below the branchings. There seems ? 
tendency to a viviparous condition ; one plant in Mrs. Gray's Herbarium 
