CERAMIUM. 161 



membranaceous, adhering to paper. Favella sessile on the margin of the 

 branches, surrounded by two or three short subuhite ramuli ; tetraspores 

 imbedded in the tips of the branches. This genus is scarcely sufficiently 

 distinct from Ceramium, of which it has the ha1>it, and from which it chiefly 

 differs in the more opake frond. The structure is very similar. 



in. Ceramium. Roth. [Plate 22, C] 



Frond filiform, one-tubed, articulated ; the dissepiments 

 coated with a stratum of coloured cellules, which sometimes 

 extend over the surface of the articulation. Fructrficaiion : 

 1, sessile, roundish fa vella, having a ])elliicid limbus, con- 

 taining minute, angular spores, and subtended by one or 

 more short, involucral ramuli : 2, tetraspores either immersed 

 in the ramuli, or more or less external. — Name, from nspa/xoi, 

 a pitcher ; but the fruit is not pitcher-shaped. 



Section 1. Rubra. Smooth ; the whole surface of the arti- 

 culation covered with coloured cells. 



1. C. rtibrtim, Huds. ; filaments robust, gradually attenu- 

 ated, irregularly dichotomous, having lateral, forked or mul- 

 tifid ramuli, the apices hooked inwards ; articulations coated 

 with coloured cellules, unarmed, the lowermost twice as long 

 as broad, the upper shorter than their breadth ; dissepiments 

 constricted ; tetraspores immersed in the articulations, whorl- 

 ed ; favella3 globose, mostly borne on the lateral branchlets, 

 subtended by three or four involucral ramuli. Harv. Phyc. 

 Brit. I. clxxxi. ; Hook. Br. Fl. ii p. 336 ; Wyait, Alg. Daiim. 

 No. 42. Conferva rubra, E. Bot. t. 1166. 



On rocks, stones, and Algte in tide-pools; also dredged in 4 — 5 fathoms. 

 Annual. Summer and Autumn. Very abundant on the Brit'sh coasts. — 

 Frond 2 — 12 inches long, robust, very variable in ramification ; when grow- 

 ing in favourable situations of a clear red colour, but oflen much faded, 

 brownish or yellow. Sometimes the lateral ramuli are all secund ; some- 

 times there are scarcely any, and sometimes they are very numerous. 



2. C. hotryocarpum. Griff. ; filaments crooked at the base, 

 robust, gradually attenuated, irregularly dichotomous, having 

 numerous lateral, mostly simple ramuli, the ajiices straight ; 

 articulations coated with coloured cellules, unarmed, the 

 lowermost twice as long as broad, the upper shorter than 

 their breadth ; dissepiments constricted ; tetraspores im- 

 mersed in the articulations, whorled ; favellaj globose, of 

 small size, heaped together in irregular clusters, borne on the 



