CERAMIUM. 161 



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

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

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

 distinct from Ceramium, of which it has the habit, and from which it chiefly 

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



III. 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. Fruetification : 

 1, sessile, roundish favellce, having a pellucid limbus, con- 

 taining minute, angular spores, and subtended by one or 

 more short, involucral ramuli : 2, tetraspores either immersed 

 in the rarnuli, or more or less external. Name, from xepa^og, 

 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. ritbrum, Huds. ; filaments robust, gradually attenu- 

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

 tifid ramuli, the apices hooked inwards ; articulations coated 

 wilh 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. t. clxxxi. ; Hook. Br. Fl. ii p. 336 ; Wijatt, Alg. Danm. 

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



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

 Annual. Summer and Autumn. Very abundant on the British coasts. 

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

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

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

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



2. C. botryocarpum, Griff. ; filaments crooked at thfc base, 

 robust, gradually attenuated, irregularly dichotomous, having 

 numerous lateral, mostly simple ramuli, the apices 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 ; favellae globose, of 

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



M 



