V. SPYRIDIACE^. 203 



tapering to the base and apex, naked for an inch or two above the base, afterwards 

 very densely set with lateral branches, which are many times decompound, with 

 several series of lesser branches and raniuli. Ramuli tapering remarkably to the 

 base and apex ; the alternate ones very slender, setaceous, attenuated. Colour a 

 brilliant carmine. Substance elastic, shrinking in drying. It closely adheres to 

 paper. 



The American specimens, here described, closely resemble those from Europe. 



Order XII. SPYPJDIACE^. 



Spyridiece, J. Ag. Sp. Gen. and Ord. Algarum, vol. 2, p. 337. Part of Cera- 

 miacece, J. Ag. a7id And. Harv. Man. Ed. 2, p. 156. 



Diagnosis. Rosy or brown-red sea-weeds, with a filiform, articulate, monosiphonous 

 frond, partially or entirely coated with small cellules. Conceptacles external, fur- 

 nished with a closed, cellular pericarp, containing numerous nucleoli, formed by the 

 transformation of spore-threads radiating from a placenta : these spore-threads are 

 much branched, articulated, and produce in their upper cells, by repeated divisions of 

 the endochrome, numerous oblong spores, which are at length massed together 

 without order. Tetraspores external, on the rameUi. 



Natural Character. Root an expanded disc. Fronds filiform, articulated, the 

 tube coated externally by a stratum of small, polygonal coloured cellules, which at 

 length conceal the articulations, except in the young branches. Stem much 

 branched, alternately or pinnately compounded, all the lesser divisions clothed 

 with minute, setaceous ramelli. Ramelli simple, pellucidly articulate, or coated at 

 the nodes with small cellules. 



Conceptacles external, pedicellate, roundish or lobed, formed by the metamorphosis 

 of one of the smaller branches. Pericarp closed, formed of a stratum of polygonal 

 cells. Its contents are thus described by Prof J. Agardh : " Placenta central, con- 

 tinuous from the peduncle, and prolonged to the apex of the cavity, formed of 

 dense, dichotomo-fastigiate and anastomosing filaments woven together. From this 

 central column of the conceptacle issue filaments (as it were branches) radiating in 

 all directions, many of them elongated and sterile, some shorter and fertile. The 

 sterile filaments are nearly regularly dichotomous, articulated, passing off at the 

 apices into the pericarpal cells ; the fertile form many fascicles, directed to the 



D D 2 



