204 BRITISH SEA-WEEDS. [^Rhodosjoermea. 



Mrs. Gulson on the Warren, opposite Exmouth, growing 

 luxuriantly on other Alg?e. Obtained on the east coast of 

 Ireland, but not in Scotland. 



MicroclacUa bears some resemblance to Ceramium ruhrnm, 

 but it has no external joints. The structure of it, as 

 described in Phjc. Brit., PI. xxix., is very curious. 



Genus XLIII. PTILOTA, AgardL 



Gen. Cliar. Frond inarticulate, linear, compressed, or flat, 

 distichous, pectinate-pinnate ; the pinnules sometimes articulate. 

 Fructification of two kinds, on distinct individuals : 1, tetraspores 

 attached to, or immersed in, the ultimate pinnules ; 2, roundish, 

 clustered receptacles (favella?) surrounded by an involucre of 

 short ramuli. — Ftilota, from a Greek word, signifying pinnated. 

 — Uarvey. 



1. Ptilota plumosa, Ag. (Plate YIII. fig. 30, a branch, 

 and to the right, a pectinated pinnule, magnified.) 



Hab. On the stems of Laminaria d'lfj'itata. Perennial. 

 Summer and autumn. Common. 



Tliis is a very handsome plant, and a general favourite. 

 It is very common in Scotland. In England it is rare, and 

 even unknown on the southern shores. It is a very variable 

 plant. Some of our finest specimens were brought to us by 



