218 CERAMIACEJ]:. V; 



nodes very short, not swollen, except the fertile ones. Favellce lateral on the upper 

 branches, not on lateral ramuli, subtended by two or three ramuli which at first are 

 short, but afterwards lengthen and divide dichotomously, and then the favellaj seem 

 sittino- in a nest of branches. Tetraspores large and very prominent, bursting 

 singly or in clusters from the outer margin of the nodes, especially those of the 

 upper divisions. Colour, a brownish purple. Substance, flaccid, adhering to paper. 

 Our var. /3 is a very remarkable form, and at first I looked upon it as a distinct 

 species, but a further comparison of numerous specimens leads me to regard it as 

 being merely an extreme variety. I have received it from several correspondents. 



The reference to Agardh, whose plant comes from the Baltic Sea, requires con- 

 firmation, as I have seen no authenticated specimen. As a species our American 

 plant is allied to C. diaplianum, from which it differs in size and in the mode of 

 fruiting ; and to C . fastigiatum and tenuissimum, from which the shorter internodes, 

 unswoUen nodes and more robust filaments separate it. 



Plate XXXIII. B. Fig. 1. GKHAMmM. arachnoideum-, ^ patentissimum ; the natural 

 size. Fig. 2, part of a branch, magnified. Fig. 3, some of the nodes and internodes, 

 highly magnified. 



9. Ceramium hyssoideum ; filaments exceedingly slender ( 5^ of an inch in 

 diameter), soft, dichotomous ; forks distant below, approximate above, the branches 

 erecto-patent with acute angles ; the upper branches having a few level-topped, 

 forked, lateral ramuli ; internodes hyaline, those of the principal stems six or eight 

 times as long as broad, of the lesser thrice as long as broad, of the ramuli very 

 short ; internodes banded, definite, swollen, especially the upper ones ; fruit 

 unknown. 



Hab. Parasitical on Gorgonia?, at Key "West, W. H. H. No. 77. (v. v.) 



Tufts about an inch high, exceedingly soft. Filaments of almost cobwebby fineness, 

 repeatedly and pretty regularly dichotomous, the axils all narrow and angles acute. 

 Lateral ramuli on my specimens few. Nodes of the ramuli greatly swollen, bead- 

 like, much thicker than the internode ; those of the older branches less so, dark 

 purple. Colour of the tuft ratlier pale. 



This is by mucli the most slender of the genus. Cer. gracillimum, when placed 

 beside it on the table of the microscope, looks large and coarse in comparison ; nor 

 is there the difi'erence in diameter between the main branches and the ramuli, so 

 observable in that species. 



IV. PTILOTA. Ag. 



Frond cartilaginous, compressed, two-edged, decompound, pectinato-pinnate, 

 distichous, opaque, having an articulated, monosiphonous axis enclosed in a thick 



