MARINE ALG^ OF BEAUFORT, N. C. 517 



numerous minute carpospores somewhat fasciculately radiating from a central point and 

 tightly inclosed by gelatinous material. 

 About 25 species in warm seas. 



KEY TO SPECIES. 



a. Frond terete or slightly flattened, dichotomously branched x . H. agardhii (p. 517). 



aa. Frond with broad, flattened, central axis and main branches and rather terete or slightly 



flattened secondary branches, laterally branched 2 . H. floresia (p. 518). 



aaa. Frond flat, expanded, borne on a short stipe, simple or giving off several lobes from 



near the base, sometimes proliferous from the margins. . . . .6. 



b. Frond gelatinous-fleshy, moderately thick, surface appearing roughly papillate under 



microscope, many starlike ganglia plainly visible below surface 3. H. gelinaria (p. 518). 



66. Frond firm membranaceous, thin, surface smooth, few starlike ganglia visible below 



surface, color purplish pink 4 . //. floridana (p. 519). 



i. Halymenia agardhii De Toni. PI. CXII, fig. i. 



Isymenia flabellata, J. Agardh, 1899, p. 66. 

 Halymenia agardhii, De Toni, 1905, p. 1542. 

 A. A. B. Ex. No. 80 (Halymenia decipiens). 

 P. B.-A. No. 647 (Halymenia dedpiens). 



Frond terete or flattened, 5 to 20 cm. tall, 2 to 10 mm. in diameter, dichotomously decompound, 

 often with a few short dichotomous proliferations, gradually tapering toward the apices, branches rather 

 erect and spreading above, rounded sinuses, habit usually dense, fan-shaped, apices obtuse, inner fila- 

 ments more or less abundant, intermixed with jelly, irregularly branched, anastomosing, segmented, 

 forming more or less long, cylindrical, or short, somewhat rounded cells; tetrasporangia scattered over 

 the surface among the cortical cells, inconspicuous; cystocarps immersed in the inner cortex, forming 

 no swellings on the surface, appearing as small, 'inconspicuous dots scattered over the frond; texture 

 rather gelatinous; color yellowish pink to dark, purplish pink. 



Florida; West Indies; Bermuda. 



Two fruiting plants dredged from coral reef offshore, Beaufort, N. C., August, 1915, occasional on 

 Bogue Beach, summer and autumn, sometimes fruiting. 



In typical specimens of this species the dichotomies are frequent, becoming more numerous toward 

 the tips, forming a dense habit with the upper branches crowded, the apices are rounded, and the internal 

 filaments are fairly numerous and usually of uniform diameter. But apparently there is considerable 

 variation among authentic specimens in the size of the plants, the acuteness of the apices, and the 

 amount of spreading of the ultimate branches. 



The specimens here referred to this species vary in habit and somewhat in structure . In some the 

 branching is profuse, forming the dense habit given as characteristic of the species, but in others this 

 is distant, forming an open habit. The apices are sometimes rounded, but are more often acuminate, 

 the same specimen sometimes having some branches rounded and others acuminate. The internal 

 filaments may be fairly numerous, but are often sparse. While, therefore, some of the plants do not 

 have all the characters given as typical for the species, authentic specimens themselves vary in these 

 respects. It may be that, in the present case, two species are confused, but it has seemed impossible 

 to separate the specimens into two groups. It has been mentioned that Dictyota dichotoma, growing under 

 different conditions, may vary in the acuteness of the apices and may assume habits described for different 

 forms and even different species. No study has yet been made of H. agarhdii in this respect, and we do 

 not know enough of the influence of the environment on its form to warrant the separation of species on 

 slight, variable differences in habit. . . 



This species may easily be mistaken for members of other genera reported from Florida, and there- 

 fore liable to be cast on our coast. It closely resembles Halarachnion ligulatum (Woodw.) Kuetz. The 

 latter species has a more generally open habit, more acute apices and fewer internal filaments than 

 Halymenia agardhii, but, as has been mentioned, the latter species may itself vary in these respects. 

 The essential distinction between these species can be made only by the characters of the genera, in that 

 Halarachnion forms its auxiliary cells and cystocarps on the primary filaments, while Halymenia forms 

 these on special secondary branches. 



