MARINE ALGA! OF BEAUFORT, N. C. 477 
KEY TO GENERA, 
Frond terete, dichotomous, cartilaginous. ............. 2... cee cee eee eens 1. Gymnogongrus (p. 477). 
Frond parasitic, appearing from the exterior as a cushionlike nemathecium on Gymnogongrus. 
SERN Wea PARE Se 8 AG JER ROMER MES He cnn NR eee Par ie RBM OREN LD Ue 2. Actinococcus (p. 477). 
Genus 1. Gymnogongrus Martins. 
Gymnogongrus, Martins, 1833a, 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 rounded 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 griffithsie (Turner) Martins. Pl. XCV, fig. 3. 
Fucus oriffithsig, Turner, 1808, pl. 37. 
Gymnogongrus griffithsia, Martins, 1833, Pp. 27. 
Gymnogongrus griffithsie, De Toni, 1897, p. 242. 
P. B.-A. No. 239. 
Frond terete or slightly compressed, 1 to 5 cm. tall, slender, about 1 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, D. 177. 
Thallus parasitic, minute, living within the tissues of other Floridex, 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 alge, 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, 1901a, p. 134.) 
