PLOCAMIUM. 119 



Thrown up, probably from deep water. June to August, llfracombe, 

 Miss Hill and Mrs. Griffiths. Youghal, Miss Hall. Root unknown. 

 Stem somewhat tuberous in its lower part, half an inch to an inch high, 

 simple or branched ; the branches suddenly expanding into broadly fan- 

 shaped, more or less deeply cleft fronds ; the segments rounded, generally 

 entire, sometimes minutely ciliate ; the tips and sometimes the margins of 

 the segments much thickened, producing oblong or oval cartilaginous 

 bodies, one or two lines in diameter, at first smooth, afterwards ciliate, and 

 which, on being dissected, are found to contain innumerable minute gra- 

 nules. No fructification, except these bodies be such, has been detected. 

 The substance is much thicker and the reticulation larger than in N. Bon- 

 nemaisoni, which it most resembles ; and I agree with Mrs. Griffiths in 

 regarding it as distinct from that species, although the differences are dif- 

 ficult to be expressed in words, and in the absence of fructification its true 

 relations cannot be determined. In outline it very much resembles some 

 states of Rhodymenia Palmetto,, but the structure is totally dissimilar. 

 Mrs. Griffiths has favoured me with the following remarks : "This plant 

 was known to Mrs. Hare thirty years since, who called it Fucus Halensis, 

 I have been told, but I do not think it ever was published. Dr. Greville 

 described it in his Crypt. Flora as identical with J!V. JBonnemaisoni, which, 

 after having known this plant upwards of twenty years, .and the other 

 nearly as long, I cannot allow. I have never seen any sort of fruit, except 

 the large wart-like substance of the tips in mature age be such ; they, 

 when very old, appear to have a fringed margin. When wetted and cut 

 through under a glass, they are full of minute grains which pour out and 

 cloud the drop of water. The colour, when fresh, is rose-red, but fresh wa- 

 ter turns it a most beautiful orange. The substance is thicker than in 

 most, but the stem and branches are also striking. I never saw it growing, 

 nor in plenty, but a few fragments may be found most tides thrown up. 

 The N. Bonnemaisoni is sometimes found near it, but rarely." Griff, 

 in lift. 



III. PLOCAMIUM. Lamour. [Plate 15, C.] 



Frond pinky-red, linear, compressed or flat, ribless, or 

 faintly nerved, cellular, distichously much branched ; the ra- 

 muli "alternate or secund, acute. Fructification of two 

 kinds : spherical tubercles (coccidia), sessile or stalked, mar- 

 ginal or axillary, containing a mass of angular spores : 2, 

 lateral or axillary, simple or branched, pods (stichidia) , con- 

 taining a double or single row of transversely parted, oblong 

 tetraspores. Name, 7rxo*a/*of, intertwined hair ; alluding to 

 the finely branched fronds. 



1. P. coccineum, Huds. ; frond narrow, cartilaginous, pia- 

 no-compressed ; branches irregularly alternate, patent ; ra- 

 muli subulate, secund, three or four consecutively, pectinate 

 on their inner edges ; tubercles lateral, sessile ; stichidia 

 scattered, simple or branched. Grev. Ala. Brit. p. 98, t. 12 ; 



