514 BULLETIN OF THE BUREAU OF FISHERIES. 



ing one or two gonimoblasts divided into several rounded lobes successively developed 

 and forming numerous angular carpospores inclosed by a hyaline sack, pericarp lacking. 



About 65 species, all marine, generally distributed. 



The genus is easily recognized by the dichotomous frond consisting of a central row 

 of large cells, with a cortical layer inclosing the nodes or extending over the entire thallus 

 and usually with forcipate tips, but the species are often difficult of determination. Few 

 species have been found in this region, and the two of these that are certainly determin- 

 able are usually easily recognized. 



KEY TO SPECIES. 



a. Cortex covering the entire frond 2. C. rubrum (p. 514). 



aa. Cortex confined to band surrounding each node, internodes naked b. 



b. Tetrasporangia occurring singly at the nodes in secund series or two to four together in a 



semicircle i. C. tenuissimum (p. 5 14). 



bb. Tetrasporangia occurring in single circles surrounding the nodes 3. C. strictum (p. 515). 



1. Ceramium tenuissimum (Lyngbye) J. Agardh. 



Ceramium diaphanum var. tenuissimum, Lyngbye, 1819, p. 120, pi. 37, B, f. 4. 



Ceramium tenuissimum, J. Agardh, 1851, p. 120. 



Ceramium tenuissimum, Harvey, 1853, p. 216. 



Ceramium tenuissimum, Farlow, 1882, p. 138. 



Ceramium tenuissimum, De Toni, 1903, p. 1450. 



P. B.-A. Nos. 497, 798, 1298, 1898. 



Frond capillary, of uniform diameter, forming more or less dense tufts usually 2 to 10 cm. high, 

 regularly dichotomously decompound with short, lateral branches scattered here and there, branches 

 erect, spreading, apices forcipate", lower segments 3 to 6 diameters long, nodes slightly swollen, cortex 

 confined to a band surrounding each node and extending for a short distance over the internodes, remain- 

 der of internode naked; tetrasporangia occurring singly on the outer side of the upper nodes in secund 

 series or, less often, two to four together forming more or less of a semicircle at the nodes, immersed in the 

 cortical layer, often protruding and prominent; cystocarps lateral near the apices, surrounded by a few 

 short, simple, incurved branches; texture slightly rigid; color purplish or reddish pink. 



Temperate waters generally. 



Occasional on other algae, Bogue Beach, Beaufort, N. C., summer and autumn, fruiting. 



Here are placed, with some doubt, several small, rather uncharacteristic specimens whose characters, 

 as far as they are shown, seem to agree with this species. These are 0.5 to 3 cm. tall, and bear tetraspor- 

 angia usually singly, protruding, inclosed by a cellular covering. Both tetrasporangia and cystocarps 

 are abundant, even on plants only 0.5 cm. tall. The characters of these specimens would, perhaps, 

 agree equally well with those of C. fastigiatum, but it may be questioned if these two species are really 

 distinct. With the exception of a single plant, all the specimens of Ceramium which have been found 

 here during the summer and autumn may, perhaps, be referred to this species, but it is possible that 

 some or all of these may be reduced summer forms of C. strictum. 



2. Ceramium rubrum (Hudson) Agardh. PL CXI, fig. 2. 



Conferva rubra, Hudson, 1762, p. XXVII. 

 Ceramium rubrum, Agardh, 1817, p. 60. 

 Ceramium rubrum, Harvey, 1853, p. 213. 

 Ceramium rubrum, Farlow, 1882, p. 135. 

 Ceramium rubrum, De Toni, 1903, p. 1476. 

 P. B. A. Nos. 345, 646. 



Frond robust, tapering toward the apices, 5 to 40 cm. tall, dichotomously decompound with short, 

 sometimes numerous, lateral branches; branches subfastigiate or spreading, apices usually forcipate, 

 nodes often contracted, lower segments 2 to 3 diameters long, cortex covering the entire frond, moder- 

 ately thick below, thinner above, more or less obscuring the nodes; tetrasporangia immersed among the 

 cortical cells at the nodes, forming one or two circles surrounding the nodes or occurring without order, 

 rather prominent; cystocarps occurring singly or in pairs on the upper branches, surrounded by a few 

 short, incurved branches; texture rather rigid; color dull reddish. 



