40 DICTYOSIPHON. 



Near low-water mark, growing on rocks or Algae. Annual. Summer. 

 Frequent on the shores of England and Ireland. Jersey. Fronds solitary 

 or tufted 624 inches in length, filiform, either pretty regularly dichoto- 

 moup, or alternately branched ; the branches forked. Ramuli more or 

 less abundant, irregularly scattered. Apices acute or acuminate. The 

 warts of fructification densely cover the whole frond, giving the branches 

 a beaded appearance. When young the frond is solid, but in advanced 

 age, owing to the decay of the central strata of cells, it becomes hollow. 

 Substance cartilaginous, dissolving into a slimy jelly if macerated in fresh 

 water. Colour, a yellowish or olive-brown. 



2. S. Lyngbyei, J. Ag.; frond tubular, at length distended, 

 much branched", the branches dichotomous, spreading, with 

 wide, rounded axils, much attenuated towards the apices ; 

 ramuli scattered, forked, capillary ; sori subdistant, disposed 

 in transverse lines. Harv. Pliyc. Brit. t. ccxxxvii. Spo- 

 rochnus rhizodes, @. paradoxa, Ag. i. Harv. Man. 1 ed. p. 

 27. Chordaria paradoxa, Lyngb. t. 14. Striaria Grevil- 

 liana, Pollexfen MS. 



Dredged, generally on a muddy bottom, in 4 10 fathom water. An- 

 nual. Summer. Land-locked bays on the coasts of Scotland and Ireland, 

 abundant in many places. Fronds from two to four feet long or more, 

 forming large tufts, or spreading, in society, over wide spaces, excessively 

 branched, nearly regularly dichotomous, tapering to a capillary fineness 

 towards the apices. Substance membranaceous, at first crisp and very fra- 

 gile, becoming soft in a short time. Colour, a pale olive-brown, or foxy, 

 becoming greenish olive in drying. 



VIII. DICTYOSIPHON. Grev. [Plate 7, D.] 



Root a small, naked disk. Frond filiform, tubular, 

 branched ; its walls composed of several rows of cells, of 

 which the inner are elongated, and connected in longitudinal 

 filaments ; the outer small, polygonal, forming a membrane. 

 Fructification : solitary or aggregated naked spores, scat- 

 tered irregularly over the surface. Name, hxruov, a net, and 

 ffifuv, a tube; from the tubular, reticulated frond. 



1. D. fceniculaceus, Huds. ; Grev. Alg. Brit. p. 56, t. 8 ; 

 Hook. Br. Fl. ii. p. 279 ; Wyatt, Alg. Damn. No. 205. 



Between tide-marks, on stones, or parasitic on other Alga. Annual. 

 Spring and summer. All round the coast. Fronds 1 to many feet long, 

 tufted, very much branched and bushy ; the main stem nearly a line in 

 diameter, undivided, bearing through its whole length alternate, elongate, 

 capillary branches, which again bear a second and a third series, each more 

 slender than the last, and all tapering at the extremity. Fructification rare. 

 Colour yellowish olive or rusty brown. 



