MARINE ALGH OF BEAUFORT, N. C. 487 
Family 2. RHODYMENIACEZ (Neegeli) Harvey. 
Thallus terete, compressed or flat, solid or hollow, or with inflated portions, usually 
erect, less often horizontally expanded, usually furcately or laterally branched, some- 
times variously proliferate or lobate, structure usually cellular; tetrasporangia embedded 
in the outer cortex, scattered over the surface or confined to nematheciumlike, thickened 
portions, usually cruciately, more rarely triangularly or zonately divided; antheridia 
variously formed; carpogonia closely associated with cells which, after fertilization, form 
the auxiliary cells; cystocarps rather prominent, pericarp thick, usually opening by an 
apical pore, free or joined to the basal placenta by filamentous strands, gonimoblast 
more or less compact, divided into several lobes formed simultaneously or successively 
and arising from a large stalk cell situated in the middle of the placenta, forming 
carpospores from nearly all the cells. 
Nearly 200 species, in nearly all seas, especially in warmer regions, but some in 
Arctic waters. 
KEY TO GENERA 
a rondisolidgerect whattesed) etl caysa. shivers sie tisrcie So epaste nhl. «eal deh SAL ieee ke Pa eR dE b. 
b. Tetrasporangia situated in definite swollen regions of the thallus... . 1. Rhodymenia (p. 487). 
bb. Tetrasporangia borne in sori scattered over the surface................. 2. Agardhinula (p. 488). 
Qa. Trond Hollow, tibular, terete or slightly fattened ops s o. c gs Seep win wc visas ib tw ca we eiee sec ce 
c. Tetrasporangia cruciately divided; frond hollow in certain regions or throughout 
ESM aaS Eis Senin piserSe TION hivakiokicacidet ovuntareotee eee s oh Leche tees 3. Chrysymenia (p. 489). 
cc. Tetrasporangia triangularly divided; frond hollow throughout, segmented by constric- 
tions here and there, sometimes with transverse diaphragms. .......... 0.220600 cee ee eeu d. 
d. Frond hollow throughout, lacking transverse diaphragms. .. ine ..4. Lomentaria (p. 491). 
dd. Frond hollow, but segmented by transverse diaphragm at the canstrictions; pericarp 
WALH) APICAL MOLE ahs wlas, <cactch esis Nelels bole sielosiee’s «fiitia)atelaene talste aires 5. Champia (p. 492). 
Genus 1. Rhodymenia Greville. 
Rhodymenia, Greville, 1830, pp. XLVIII, 84. 
Frond flat, dichotomously or palmately divided, often with prolizerations from the 
margins, usually stalked below; structure cellular, central axis lacking, medullary cells 
fairly large, oblong, crowded, cortical cells minute, vertically subradiate; tetrasporangia 
usually confined to definite regions of the thallus, which are sometimes swollen like 
nemathecia, embedded among the cortical cells, cruciately divided; antheridia forming 
superficial sori consisting of single layers of minute, hyaline, vertical cells; cystocarps 
scattered over the frond, hemispherical, opening by an apical pore, fruiting cavity not 
filled by a filamentous network, gonimoblast inconspicuously lobate, arising from the 
base of the cavity, the young lobes composed of segmented filaments, the mature ones 
having many rotund carpospores irregularly grouped in masses, somewhat inclosed by 
a gelatinous covering. 
About 20 species, widely distributed. 
Rhodymenia palmetta (Esper) Greville. Pl. CI, figs. 3 and 4. 
Fucus palmetta, Esper, 1797, p. 84, pl. 40. 
Rhodymenia palmetta, Greville, 1830, p. 83, pl. 12. 
Rhodymenia palmetta, De Toni, 1900, p. 514. 
Frond flat, decompound-dichotomous, 1 to 20 mm. wide, 2.5 to 18 cm. tall, cuneate at the base, 
flabellately expanded above, often supported by a cartilaginous stipe 0.3 to 0.7 mm. wide, 1 to 35 mm. 
long, gradually passing into the widened frond, segments linear, margins smooth, apices acuminate or 
rotund; tetrasporangia forming single, rounded sori in slightly swollen portions of the frond below the 
