60 RHODOMELACE^. v. 



as lono- as broad ; apices bluntish ; stichidia lanceolate-acuminate, on the lower forks 

 oftheramelli. Polyslphonia Gibbesii, Harv. MSS. in Herb. Gibbes. (Tab. XV. A.) 



Hab. At Key West, abundant. Dr. Wurdeman, Prof. Tuomey (27), W. H. H. 

 (8), &c. (v. V.) 



Root a small disc. Fronds tufted, 4-8 inches high, half a line to nearly a line in 

 diameter in the middle, and tapering to the base and apex, distichously much 

 branched. Stem undivided, slightly zigzag, naked for an inch or more above the 

 base, thence upwards furnished at intervals of about half an inch with several 

 alternate branches, much narrower than the part from whence they spring, the 

 loAver ones long, and again compounded, the upper gradually shorter. Branches in 

 circumscription obovate, fastigiate, round-topped, twice or thrice pinnated ; the 

 pinnules dichotomous, with rounded angles, their ultimate divisions resolved into 

 single-tubed, many times dichotomous ramelli. The stem and branches are com- 

 pressed, coated with polygonal cells, inarticulate, with a medial row of minute 

 dark coloured, transverse lines, a quarter of a line apart and visible to the naked 

 eye, or with a pocket lens. These lines are the nodes of the central tube of the 

 axis of the frond. The pinnules are cylindrical and articulate, polysiphonous and 

 somewhat veiny in their lower parts, few-tubed in the upper, and at length passing 

 into the single-tubed ramelli. The stichidia are numerous on the lower forks of the 

 ramelli ; several on the same ramellus ; they are pedicellate, oblongo-lanceolate, 

 acuminate, and contain a triple series of large tetraspores. Conceptacles unknown- 

 Colour a purplish lake, growing darker and browner in drying. Substance of the 

 stem and branches cartilaginous, of the ramelli soft and tender. In drying, the 

 plant adheres pretty firmly to paper. 



A beautiful species, unlike any other North American one, but allied to D. Gun- 

 nia7ia and D. Laivrenciana of Tasmania, from both Avhich, however, it is abundantly 

 distinct. The name is given in honour of Prof. Lewis R. Gibbes of Charleston) 

 from Avhom I received the first specimen of this and several other interesting Algte 

 of Florida. 



Plate XV. A. Fig. 1. Dasya Gibbesii ; the natural size. Fig. 2, apex of a lesser 



branch with terminal ramelli and stichidia ; /ir/. 3, a stichidium •,fig. 4, a tetraspore ; 



fig. 5, portion of a ramellus ; fi.g. 6, part of the stem, to show surfiice cellules, and 



medial, dark striaj ; fig. 7, longitudinal section of the same through the smaller 



diameter ; fig. 8, transverse section ; all more or less magnified. 



Subgenus 2. Rhodonema. Frond inarticulate or rarely articulate, cylindrical, 

 irregularly branched ; branches more or less completely clothed on all sides with 

 dichotomous, single-tubed, confervoid ramelli. Stichidia glabrous. 



2. Dasya (Rhodonema) elegans., kg.; frond very soft and flaccid, soon decom- 

 posmg ; stem robust, inarticulate, elongate, alternately decompound ; branches 

 fihform, of unequal length, undivided, all the younger parts clothed with byssoid. 



