MARINE Al^JB, OF BEAUFORT, N. C. 477 



KEY TO GENERA. 



Frond terete, dichotomous, cartilaginous i . Gymnogongrus (p. 477). 



Frond parasitic, appearing from the exterior as a cushionlike nemathecium on Gymnogongrus. 



2 . Actinococcus (p. 477). 



Genus i. Gymnogongrus Martins. 



Gymnogongrus, Martins, 18333, p. 27. 



Frond terete or flattened, repeatedly dichotomous, often also with more or less 

 numerous lateral branches, of fleshy-leathery or horny consistency; tetrasporangia 

 unknown; procarps borne on fertile upper segments of the frond in flattened promi- 

 nences; cystocarps immersed in the frond, more or less prominent on one or both sides; 

 containing a compound "nucleus" bearing numerous rotinded carpospores without order 

 among sterile filaments; fruit entirely inclosed; at length freed by the formation of one 

 or more pores. 



About 35 species, widely distributed, especially in warm and temperate seas. 

 Gymnogongrus griffithsise (Turner) Martins. PI. XCV, fig. 3. 



Fucus griffithsice. Turner, 1808, pi. 37. 

 Gymnogongrus griffithsia, Martins, 1833, p. 27. 

 Gymnogongrus griffithsia, De Toni, 1897, P- 242. 

 P. B.-A. No. 239- 



Frond terete or slightly compressed, i to 5 cm. tall, slender, about i mm. in diameter, several stems 

 arising from a rootlike callus, branching dense or sparse, usually regularly dichotomous, often poly- 

 chotomous and with irregular pinnate branches, main branches unbranched below, richly branched 

 above, forming dense tufts at the apices; substance cartilaginous, color dark purple, becoming blackish 

 when dry. 



North Atlantic and Pacific Oceans; Mediterranean Sea. 



Abundant on Fort Macon jetties, Beaufort, N. C., about 15 cm. above to 15 cm. below low water, 

 throughout the year; occasional on Bogue Beach and in harbor. 



Specimens from different localities vary in height and diameter of fronds, amount of branching, 

 and amount of flattening. Those from this region are fairly uniform, being 2.5 to 3.5 cm. tall, and 

 comparatively thick, rigid, and terete. 



Genus 2. Actinococcus Kuetzing. 

 Actinococcus, Kuetzing, 1843, p. 177. 



Thallus parasitic, minute, living within the tissues of other Florideae, and forming 

 fruiting cushions on the surface of the host plant ; vegetative portion consisting of fila- 

 ments penetrating the host and winding about among the cells of the frond; fruiting 

 cushions more or less hemispherical or flattened-convex, strongly attached to the host, 

 composed of fanlike radiating filaments, with cells gradually decreasing in size toward the 

 periphery ; tetrasporangia numerous in the cortical layer of the nematheciform cushion, 

 moniliform serrate, cruciately divided, arising from the transformation of the cells 

 (usually with the exception of the 2 to 4 apical ones) of the radiating filaments; anthe- 

 ridia and cystocarps unknown. 



Four to five species recognized, occurring on different genera of algae, mostly on 

 species of Gymnogongrus. 



The members of this genus were originally taken for the tetrasporic fruits of their 

 hosts. "Several genera of this character have been described. It is a curious fact that 

 in each case the parasite has tetrasporic fruit of the character appropriate to the host, 

 while the host appears to have lost the capacity for producing tetraspores, and is propa- 

 gated either by cystocarps or only vegetatively." (Collins, igoia, p. 134.) 



