146 POLYIDES. FURCELLARIA. 



VIII. POLYIDES. Ag. [Plate 18, D.J 



Root an expanded disk. Frond cylindrical, dichotomous, 

 cartilaginous, solid ; the axis consisting of densely-packed, 

 longitudinal, interlacing and anastomosing filaments ; the 

 periphery of coloured, horizontal, dichotomous filaments, 

 whose lower half is composed of large, elliptical cells, their 

 upper half of much smaller, submoniliform cellules. Fructi- 

 fication: 1, oblong, irregular, spongy warts, composed of 

 dichotomous filaments, through which are scattered ellipsoidal 

 favellce, having a broad, pellucid limbus ; 2, cruciate tetra- 

 spores immersed among the filaments of the periphery of the 

 frond. Name from sroxv, many, and idea, form or appearance. 



1. P. rotundus, Gmel. ; Grev. Alg. Brit. p. 70, t. 11; 

 Hook. Br. Fl. ii. p. 284 ; Wyatt, Alg. Danm. No. 161 ; Harv- 

 Phyc. Brit. t. xcv. Fucus rotundus, E. Bot. t. 1738. 



On rocks and stones in the sea. Perennial. Autumn and winter. 

 Southern and Eastern shores of England and Ireland. Bather rare in 

 Scotland. Root an expanded disk. Fronds 4 6 inches high, as thick as 

 whip-cord, of a dark purplish brown colour, terete, repeatedly dicholo- 

 mous, the tips fastigiate, giving the plant a rounded outline when displayed ; 

 the axils rounded. Fructification : " spongy pale or pink warts on the 

 sides of the upper branches, at first roundish or oblong and scattered, but 

 at length 2 4 lines long and 1 or 2 lines thick, sometimes creeping all 

 round the frond, and occasionally several, becoming confluent, extend for 

 nearly an inch along the branches. The warts are naked or destitute of 

 any epidermis, composed of white articulate filaments, radiating horizon- 

 tally from the frond, and containing numerous imbedded clusters of spores 

 (favellce), each cluster surrounded by a pellucid limbus." Grev. Besides 

 this fructification, Mrs. Griffiths communicates specimens from Sidmouth 

 having the upper ramuli slightly swollen and containing imbedded tetra- 

 spores, of a narrow shape, with the endochroine parted crosswise into 4 

 sporules. In habit this plant closely resembles the following, and can 

 scarcely be distinguished when out of fruit, except by the root and the 

 rounded axils of the branches. 



IX. FURCELLARIA. Lamou. [Plate 18, C.] 



Root branching. Frond cylindrical, dichotomous, cartila- 

 ginous, solid ; the axis consisting of densely packed, longi- 

 tudinal, interlacing and anastomosing filaments ; the peri- 

 phery of coloured, horizontal, dichotomous filaments, whose 

 lower half is composed of large ellipsoidal cells ; their upper 

 half of much smaller cylindrical cellules. Fructification 

 oblong, transversely parted or zoned tetraspores, deeply im- 

 bedded among the filaments of the periphery, in the swollen 



