510 BULLETIN OF THE BUREAU OF FISHERIES. 
aa. Thallus consisting of a monosiphonous central axis partially or entirely surrounded by 
cortical layers. 13s) .).c.1a{venatl o) seeiceh Saser ating: generat eGk Jeblao:-igas bees “Maas te ewer of Cc. 
c. Thallus laterally branched, cortex continuous throughout or lacking only on the finer 
divisions). : fisgih- seipenburleseoe carat abo dane -aMeeeas <SoMsemere lores > 4. Spyridia (p. 512). 
cc. Thallus dichotomously branched, forcipate at apices, cortex continuous or present 
only at the nodes: 05... 5 ool wn eoceeinne «GRRE chee ARES aelsa tite se 5. Ceramium (p. 513). 
Genus 1. Spermothamnion Areschoug. 
Spermothamnion, Areschoug, 1847, D. 334. 
Thallus composed of erect, naked, monosiphonous filaments arising from creeping 
filaments attached to the substratum at intervals, erect filaments oppositely or alter- 
nately branched; tetrasporangia sessile, occurring singly or in groups on short lateral 
branchlets, triangularly divided; antheridia ovoid-oblong, sessile on short lateral branch- 
lets, sometimes terminal, composed of minute hyaline cells grouped around a central 
axis; procarps usually terminal on lateral branchlets, always with two auxiliary cells; 
cystocarps globose, small, terminal on lateral branchlets, sometimes naked, usually 
inclosed by short upgrowing, filamentous branchlets, pericarp lacking, containing two 
gonimoblasts which are small, compressed, and bear numerous single, rounded carpo- 
spores radiating in all directions. 
About 15 species, in warm and temperate seas. 
Spermothamnion investiens (Crouan) Vickers. Pl. XCI, fig. r. 
Callithamnion investiens, Crouan, in Schramm and Mazé, 186s, p. 7. 
Callithamnion investiens, Crouan, in Mazé and Schramm, 1870, p. 141. 
Spermothamnion investiens, Vickers, 1905, D. 64. 
Thallus forming dense woolly tufts, closely enveloping the host plant; primary filaments creeping, 
attached to the substratum at intervals by unicellular, rhizoidal structures flattened at their ends to 
form attaching disks, secondary filaments erect, numerous, 1 to 3 mm. tall, 14 to 16 mic. wide, sparingly 
alternately branched, sometimes simple, branches usually simple, segments 30 to 100 mic. long, usually 
55 to 70 mic.; tetrasporangia occurring singly, terminating short (usually one-celled), lateral branchlets, 
borne oppositely or secundly, ellipsoid or slightly obovate, sometimes almost globose, 30 to 40 mic. 
wide, 37 to 45 mic. long; antheridia oblong-ovate, borne singly at the apices of more or less prolonged 
lateral branches or of the main filaments; cystocarps situated like the antheridia; texture velvety; color 
rose. 
West Indies. 
Occasionally very abundant on Bogue Beach, Beaufort, N. C., on about half of the specimens of 
Zonaria flava found on the beach throughout the year, fruiting at all seasons, very abundant on about 
one-third of specimens of Zonaria flava dredged off coral reef, May, 1907. 
The Beaufort plants are closely similar to Miss Vickers’s specimens from Barbados. This species 
here forms dense, velvety mats covering in almost pure growths the main stems, branches, and larger 
ribs of the Zonaria. It has been found only on this host except in one instance when a battered speci- 
men of Brongniartella mucronata on Bogue Beach had the lower part of its stem densely covered with 
filaments of thisspecies. Itseems very probable that all the plants of Zonaria flava found here have come 
from the coral reef offshore. 
It has been noted by Farlow (1882, p. 119) and Lewis (1909, pp. 683, 684) that, in S. turnert (Mert.) 
Aresch, apparent tetraspores may occur on the same individual with procarps, cystocarps, or antheridia. 
The author has, in the present species, observed cystocarps on the same filaments with what appeared to 
be undivided tetrasporangia, but has not found cystocarps and mature tetraspores on the same plant. In 
one instance there was observed a structure (fig. 42) that appeared to be an imperfectly divided tetra- 
sporangium which had continued its growth as a vegetative filament. At Beaufort the masses of Sper- 
mothamnion on some specimens of Zonaria seem to be entirely tetrasporic, but on other plants of the 
host antheridia, cystocarps, and tetraspores occur intermingled. 
