MARINE A^GJE OF BEAUFORT, N. C. 487 



Family 2. RHODYMENIACEyE (Nasgeli) 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. Frond solid, erect, flattened b. 



b. Tetrasporangia situated in definite swollen regions of the thallus i. Rhodymenia (p. 487). 



bb. Tetrasporangia borne in sori scattered over the surface 2. Agardhinula (p. 488). 



aa. Frond hollow, tubular, terete or slightly flattened c. 



c. Tetrasporangia cruciately divided; frond hollow in certain regions or throughout 



3. Chrysymenia (p. 489). 



cc. Tetrasporangia triangularly divided; frond hollow throughout, segmented by constric- 

 tions here and there, sometimes with transverse diaphragms d. 



d. Frond hollow throughout, lacking transverse diaphragms 4. Lomentaria (p. 491). 



dd. Frond hollow, but segmented by transverse diaphragm at the constrictions; pericarp 



with apical pore 5. Champia (p. 492). 



Genus i. Rhodymenia Greville. 



Rhodymenia, Greville, 1830, pp. XL VIII, 84. 



Frond flat, dichotomously or palmately divided, often with proliierations 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. PI. CI, figs. 3 and 4. 



Fucus palmetta, Esper, 1797, p. 84, pi. 40. 

 Rhodymenia palmetta, Greville, 1830, p. 88, pi. 12. 

 Rhodymenia palmetta, De Toni, 1900, p. 514. 



Frond flat, decompound-dichotomous, i 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, i 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 



