242 BUiTiSH SEA-WEEDS. [JiJiodosjjermeiS. 



Ilab. On rocky shores. Perennial. Summer and antnmn. 

 Common on the southern shores of England ; not uncom- 

 mon in Ireland. Eare in Scotland, where, however, it has 

 been found by Dr. Greville in the island of Bute; by 

 Major Martin at Ardrossan ; by D. L. at West Kilbride, 

 Ayrshire, and in the island of Arran. 



From the similarity in colour, and from some resemblance 

 in the outline, it may at times, in Scotland, have been 

 passed over as Plocamium coccineiim. It is, however, a 

 much larger plant, being a foot and a half in length. It is 

 one of the most beautiful of the British Algse. AVhen pro- 

 cured fresh, the colour is a fine rose-red. Por- excellent 

 figures, with instructive dissections, see PL xv. of ' Algce 

 Britannica3 ' of Dr. Greville, and PL lxt. of Professor Har- 

 vey's ' Phycologia Britannica.'' 



Genus LXIX. RUODYMENIA, Greville. 



Gen. Char. Prond plane, membranaceous, fine pink or red, 

 quite veinless, sessile, or with a short stem, which expands im- 

 mediately into the frond. Fructification : 1, hcmisplierieal 

 scattered capsules ; 2, minute, ternate granules, spreading over 

 the whole, or some part of the frond (not in defined spots). — 

 Name from two Greek words signifying red mernbrane. — Greville. 



