166 SPYRIDIA. 



eid, those of the middle of the stem several times longer 

 than broad, the upper gradually shorter ; dissepiments co- 

 loured, armed on the outer edge with a single robust, broadly 

 subulate, coloured, three-jointed prickle ; tetraspores erum- 

 pent, whorled round the joint; favellae roundish, subtended 

 by a solitary, incurved ramulus. Harv. Phyc. Brit. t. cxl. 

 C. ciliatum J3. acanthonolum, Harv. Man. ed. 1, p. 100. 



On exposed rocks, near low-water mark, and on the smaller Algae. An- 

 nual. Summer and autumn. Not uncommon. Very densely tufted, 2 

 6 inches high, matted when old, fastigiate when young, of a very dark 

 purple colour, rigid and harsh to the touch. Known from C. flabelliyerum 

 by its different habit, and hyaline articulations ; and from both the other 

 species of this section by its solitary spine. 



13. C. ciliatum, Ellis ; frond slender, of nearly equal dia- 

 meter throughout, rigid, repeatedly dichotomous, with or 

 without lateral branchlets, fastigiate, the apices strongly in- 

 volute ; articulations pellucid, those of the middle of the 

 stem from three to four times as long as broad, the upper 

 gradually shorter ; dissepiments coloured, furnished with a 

 whorl of robust, subulate, three-jointed prickles; tetraspores 

 alternating with the prickles ; favellae subtended by two or 

 three ramuli. Harv. Phyc. Brit. t. cxxxix ; Harv. in Hook. 

 Br. Fl. ii. p. 336 ; Wijatt, Alg. Danm. No. 180. Conf. ci- 

 liata, Ellis. E. Bot. t. 2428. 



On rocks and stones, and on the smaller Alga? in tide-pools. Annual. 

 Summer. Not uncommon. Forming dense, fastigiate tufts of a paler 

 shade of purple than in C. acanthonotum, from which this species is at 

 once known by having numerous, whorled prickles on each joint. A beau- 

 tiful object under a low power of the microscope. 



IV. SPYRIDIA. Harv. [Plate 22, D.] 



Frond filiform, cylindrical, much branched, traversed by 

 a wide, articulated tube, whose walls are composed of small 

 angular cells ; ramuli setiforrn, simple, jointed. Fructifica- 

 tion : 1, stalked, gelatinous, lobed favellte, involucred by 

 short ramuli, and containing two or three distinct masses of 

 roundish spores ; 2, external tetraspores, with colourless bor- 

 ders, attached to the ramuli. Name, Swapis, a basket ; in 

 allusion to the appearance of the receptacles. 



1. S. filamentosa, Wulf ; frond irregularly branched, sub- 

 opake ; branches tapering at the base, more or less densely 

 clothed with setaceous ramuli ; articulations of the stem very 



