<l5 



V. RHODYMENIACE^. 147 



VI. CoRDYLECLADiA. Conceptacks external, sessile. Tetraspores cruciate, lodged in 

 proper, pod-like ramuli. 



I. RHODYMENIA. Grev. 



Frond flat, membranaceous, dichotomous or palmate, often proliferous from the 

 margin or disc, composed of two strata of cells ; the inner cells oblong, the superfi- 

 cial minute, in few vertical rows. Conceptacks scattered over the frond, sessile, 

 hemispherical, A\ith a cellular pericarp at length opening by a terminal pore ; 

 sporiferotts filaments very numerous, emitted from a hasal placenta, and forming a 

 simple nucleus surrounded by a gelatinous pellicle. Tetraspores either collected in 

 cloud-like patches, or dispersed over the frond among the superficial cellules, 

 roundish, cruciate or tripartite. # 



This genus, as originally constituted, included a large number of plants which 

 had a resemblance in habit to each otlier, but which a more accurate examination 

 has shown to belong to several widely separated types of structure : hence the 

 genera Euthora, EhodophylUs, KaUymenia, Callophyllis^ Calliblepharis, Sarcodia, (^-c, 

 have been formed at its expence. The generic character, as here given, is that 

 fixed by Prof. J. G. Agardh. It reduces the species now placed in Rhodymenia to 

 about a dozen at the most; and, small as this number is, they naturally divide into 

 two sections or sub-genera, distinguished not less by peculiarities of fructification 

 than by minor external characters. In the first section the tetraspores are scattered 

 through the surface cellules over the whole frond ; the fronds are of large size, 

 purplish or dull-red, sub-simple or irregularly palmatifid, and the stem is but little 

 developed. In the second the tetraspores are confined to definite sori, placed 

 immediately below the ends of the lobes ; the fronds are dichotomous, of a bright 

 red or rosy, and the stem is always considerable, and sometimes branched. The 

 species of this latter section have a habit very similar to that of Pliyllopliora. 



1. Palmatce: tetraspores scattered in cloudy patches over the whole frond. 



1. Rhodtjienia pertusa, J. Ag. ; stipes short, cartilaginous, compressed, expand- 

 ing into a broadly lanceolate, sub-undivided, membranaceous, blood-red lamina (one 

 to three feet in length) attenuated at the base; conceptacles very numerous, densely 

 scattered over the surface of the frond. /. Ag. Sp. Alg. 2, p. 376. Rhodymenia 

 Willesii, Bail, and Harv. in Bot. E.rpl. Ex. cum Icone, ined. Porphyra pertusa, Post, 

 and Ritp. Alg. Ross. p. 20, t. 36. 



Hab. Straits of St. Juan de Fuca, Copt. Wilh's. (v. s.) Greenland, Wormskiold. 



u 2 



