POLYSIPHONIA. 89 



siphons six or rarely seven ; ceramidia ovate, on short stalks. 

 Ag. Sp. Alg. vol. 2, p. 81 ; Harv. Phyc. Brit. t. civ. 



On mud-covered rocks in bays and estuaries, and on Zosfera, &c. An- 

 nual. Summer and Autumn. Very local. Hitherto only found, in 

 Britain, in the neighbourhood of Plymouth, hut there abundant. — Tufts 

 dense, 4 — 8 — 10 inches long, rigid below, very flaccid, and bright purple 

 above. Filaments much branched, dichotomous, clearly articulated to the 

 base. A distinct and beautiful species, and widely dispersed. It is abun- 

 dant on the shores of France and Spain, in the Adriatic, and on the east 

 coast of North America, in several places. 



*** Frond articulated throughout ; primary tubes from eight to twenty. 



17. P. obscura, Ag. ; tufts of small size, densely matted 

 together; filaments creeping, throwing up erect, simple, se- 

 cond branches, which are either naked or furnished with 

 a few secund ramuli; articulations as long as broad, many 

 tubed; siphons 12 — 13. Ag. Sp. Alg. vol. 2, p. 108; Harv. 

 Phyc. Brit. t. c\\. A. 



On rocks, &c. at half-tide level. Jersey, Miss White. Sidmouth, Rev. 

 R. Cresswell. — Plant spreading over the surface of rocks, in patches of six 

 inches to a foot in diameter, covering the roots offuci, &c. Filaments de- 

 cumbent, attached by rootlets which issue from the lower surface, sub- 

 simple, furnished, along the upper surface, with erect, recurved branches, 

 from a quarter to half an inch in length. Articulations visible in all parts 

 of the frond. Colour a dark brown-red. 



18. V.simulans, Harv.; filaments slender, bushy, branched 

 from the base ; branches alternate, patent, repeatedly (but 

 irregularly) pinnate ; the penultimate branches long and 

 simple, set with short, distant, spine-like ramuli ; articula- 

 tions of the branches once and half as long as broad, of the 

 ramuli shorter, many tubed ; siphons about twelve ; cera- 

 midia globose. Harv. Phyc. Brit. t. cclxxviii. P. spinu- 

 losa, of Herbaria, not of Grev. 



On rocks, &c., between tide-marks. Annual ? Summer. Rare. Tor- 

 quay, Mrs. Griffiths, 1831. Valeiitia, Kerry, JV. H. //., 1845. Orkney, 

 Rev. J. H. Pollexfcn. Jersey, Miss White and Miss Turner. — " Colour 

 reddish. Substance stiff" and brittle. Stems set with spines irregularly, 

 which hold the plant together, so that it is difficult to disentangle.'' Mrs. 

 Griffiths. The ceramidia are nearly spherical, witli a wide mouth. This 

 has the habit of P. spinulosa, with which it has been hitherto confounded, 

 but it is really much more nearly related to P. nigrescens. It is, however, 

 a smaller and more slender plant, more irregularly branched, and with 

 much fewer siphons in the stem. Some of Miss Turner's specimens are 

 closely pinnated, and have something the aspect of Sphacelaria cirrhosa ; 

 but usually the main branches are distant, and irregularly set. 



19. P. nigrescens, Huds. ; filaments robust, rigid, and 

 generally rough with broken branches below, much branched 



