V. RHODYMENIACE^. 149 



leathery, not ad herin 2: to paper except after a long maceration in fresh vater. 

 Colour a deep brownish purple. 



In some specimens dredged in Halifax Harbour the frond is very much broader 

 than its length, but little divided, and having tlie margin very much waved. The 

 substance is thinner than in the common form, which occurs abundantly at Halifax. 



3. RnoDYMENiA? interrupta, Grev. ; frond membranaceous, irregularly divided, 

 sub-dichotomous ; the lacinite divaricated, linear, constricted at short intervals ; the 

 terminal lobes digitate ; axils and apices rounded. Grev. in Nov. Act. Nat. Cur. 

 xiv. p. 423, t. xxvi. Jig. 1. J. Ag. Sp. Alg. 2, p. 382. 



Hab. Arctic Sea, Lieut. W. N. Griffiths, (v. s. in Herb. CI. Dnse. Griffiths.) 



Base unknown. Frond (broken) eight or ten inches long, irregularly dichoto- 

 mous, the terminal lobes digitate or pedate. Lacinice widely spreading or divari- 

 cate, about half an inch -wide, linear, repeatedly but irregularly constricted at short 

 intervals in a nodose manner ; the margin undulate. Axils very obtuse, rounded, 

 from half an inch to an inch Avide. Apices rounded, somewhat wider than the 

 laciniie. Nemathecia wart-like, small, clustered, growing from the margin or the 

 disc of the lower segments. Substance thin. Colour a dull red, rather brownish 

 below. It does not adhere to paper. 



A thin slice shows two or three rows of large, polygonal, empty medullary cells, 

 with a thin exterior coating of coloured, minute cells, gradually smaller towards 

 the circumference. This structure is different from that of Phyllophora Brodicei; to 

 an extravagant form of which variable plant this curious species bears some resem- 

 blance. I have to express my thanks to Mrs. Griffiths for allowing me to examine 

 the single specimen brought home by her son from the Ai'ctic regions, being that 

 from which Dr. Greville's figure was made, and the only one known to exist at 

 present in any Herbarium. 



2. Palmettce: tetraspores aggregated in distinct sori below the tips of the lacinice. 



4. RpioDTivrENiA Palmetfa, Grev. ; stipes cylindrical, sub-simple, expanding into a 

 fan-shaped, rose-red frond, more or less deeply cleft dichotomously ; laciniic linear- 

 wedge-shaped, with broad rounded interstices and a very entire, flat margin ; apices 

 either erose or rounded ; conceptacles marginal or scattered ; tetraspores cruciate, 

 forming deep-red sori in the dilated apices. Harv. Phyc. Brit. t. 134. /. Ag. Sp. 

 Alg. 2,;?. 378. Sphafrococcus Palmetta, Kiitz. Sp. Alg. p. 782. Fucus Palmetta, 

 Esper. t. 40. Turn. Hist. t. 73. E. Bot. t. 1120. 



Hab. On shells and stones in deep water and on the stems of Laminariaj. Halifax, 

 W. H. H. (v. V.) 



