148 RHODYMENIACE^. v. 



Boot scutate. Fronds tufted, rising witli a compressed stem, which, at half an 

 inch to an inch from the base becomes flattened, cuneate, and gradually widens, 

 until it passes into the base of a broadly lanceolate lamina, from one to three feet 

 lono- and from four to eio;ht or ten inches wide. Lamina much attenuated at the 

 base, commonly quite simple, sometimes forked ; the newer portions formed, as in 

 Laminaria, between the apex of the cartilaginous stem and the base of the expan- 

 sion. Colour pale blood-red, fading into greenish. Conceptacks as large as poppy- 

 seed, spherical, extremely numerous, half immersed in the lamina and scattered 

 thickly through three-fourths of it, commencing at the apex and extending toward 

 the base. 



This fine species was originally published under the erroneous generic name of 

 Porphyra ; and as such it escaped the notice of Prof. Bailey and myself when, in 

 examining the Algae of Wilkes' Exploring Expedition, we proposed to give Capt. 

 "Wilkes's name to what we rightly considered a Rhodymenia, and believed to be an 

 unpublished species. Meantime, Professor Agardh having received specimens of 

 the so-called Porphyra pertusa, and at once perceiving that they were referable to 

 lihodymenia, has sanctioned the specific name pertusa in his recently published 

 Species Algarum. I am therefore constrained to adopt this name, in preference to 

 that which my friend Bailey and I had proposed. It is given by its author in allu- 

 sion to certain roundish holes often to be found in the membranes, but which 

 appear to me to be casualties, such as occur in very many of the membranous 

 Algaj, as in Ulva latissima, &c. 1 have received from Dr. Ruprecht an authentic 

 specimen of his plant, and find it identical in species with the specimens brought 

 home by Wilkes. These latter are, however, of much greater size and in more 

 perfect condition. 



2. Rhodymenia palmata, Grev. ; frond coriaceous or membranaceous, purple, 

 broadly wedge-shaped, irregularly cleft, palmate or dichotomous, sometimes repeat- 

 edly laciniate ; the margin flat and even, sometimes winged with leaflets ; tetra- 

 spores distributed over the whole frond in cloud-like spots. Harv. Phyc. Brit. t. 217 

 and 218. /. Ag. Sp. Alg. 2, p. 376. Sphcerococcus palmatus, Kiitz. Sp. Alg. p. 781. 

 Fucus palmatus. Lin. — Turn. Hist. Fuc. t. 115. E. Bot. ^. 130G. Dulse or Dillish, 

 vulg. 



Hab. Parasitical on littoral Fuci., Laminarice, etc. Halifax, W. H. H. Boston 

 Bay, Dr. Asa Gray, Mr. G. B. Emerson, etc. Long Island Sound, Prof. Bailey, 

 Mr. Hooper, etc. Common, (v. v.) 



Frond 6 — 12 inches long or more, from one to four or six inches broad, cuneate 

 at the base, and generally broadly cuneate in outline, vertically cleft in a sub-pal- 

 mate manner ; sometimes quite simple, sometimes cloven nearly to the base into 

 iiuuunerable slender ribbons. The margin is generally flat, but is often furnished 

 at intervals Avith simple or forked leaf -like lobes, giving a pinnate character to the 

 frond. Apices obtuse. Axils generally acute. Substance firmly membranous or 



