28 RHODOMELACE^. v. 



trifid or multifid at the tips, so that the tips appear to the naked eye as if capitate, 

 and dark coloured. At a later period, this character is lost by the lengthening out 

 of the cloven tips into new ramuli. Conceptacles on longish stalks, abundant on 

 the ultimate ramuli, converting them into racemes. Tetraspores unknown to me. 

 A-bundant dichotomous fibrils clothe the ends and sides of the ultimate ramuli. 

 Colour a fine red, communicating a rosy tinge to the paper on which the plant has 

 been dried, and to which it closely adheres. Substance flaccid. 



I ain disposed to keep this beautiful plant separate from R. gracilis, to which, in 

 its soft substance and slender stems, it is most nearly allied. It differs in being 

 still more slender, of a brighter colour, with more distichous habit. The pinnated 

 branching is much more definite than in either R. gracilis or R. suhfusca. The name 

 is given in compliment to Dr. M. B. Roche of New Bedford, from whom I first 

 received it, and to whom I am also indebted for many other beautiful specimens 

 of AlgEe. 



VI. RYTIPHL.EA. Ag. 



Frond filiform or compressed, decompound pinnate, transversely striate, areolated ; 

 the axis articulated, composed of a circle of large, tubular, elongated cells of equal 

 length, surrounding a central cell ; the periphery of one or more rows of small 

 irregularly shaped cells. Conceptacles ovate, pedicellate or sessile, containing a tuft 

 of pear-shaped spores on simple funiculi radiating from a basal placenta. Tetra- 

 spores contained in the terminal fusiform ramuli or in proper stichidia, in a single 

 or double row. 



The structure of the frond in this genus is very similar to that of the opaque and 

 inarticulate portions of several Polysiphonice, in which the articulated axis, composed 

 of symmetrical cells radiating round a central cavity, is coated externally with 

 numerous rows of cells irregularly shaped and placed ; of these the inner ones are 

 large and often empty, the outer gradually smaller and more constantly contain- 

 ing bags of coloured matter. The difference between the genera is almost wholly 

 technical, Polysiplionia having at least its younger portions destitute of the peri- 

 pheric layer of cells, and Rytiphlwa having these parts coated, though less perfectly 

 than the other portions. The transversely striate appearance of the Rytiphlcece, 

 which is best seen with a common pocket lens, arises from the nodes of the 

 enclosed articulated axis being visible through the coat of peripheric cells. Of 

 course, this appearance is most obvious in the younger parts, where the cellular 

 coat is less dense. The species of Rytiphla^a are few, and mostly tropical or sub- 

 tropical. 



