RHODOMELACE.E. 29 



1. Rytiphl^a? Baileyi ; frond compressed, areolated, irregularly branched; 

 branches closely bipinuate ; pinnae alternate, nearly equal, patent ; pinnulae sub- 

 ulate, subarticulate, the lowermost simple, the upper ones sometimes cloven, all 

 slightly inflexed. 



Hab. Monterey Bay, California, Prof. Bailey, (v. s. in Herb. T.C.D.) 



Frond compressed, inarticulate, two or three inches long, half a line in diameter, 

 divided near the base into several branches, which are closely bi-tripinnate through- 

 out. Pinna' not two lines asunder, very patent, half an inch to an inch long, 

 compressed, closely pinnulated with subulate slender ramuli, the lowermost of which 

 are simple and subdistant, the upper frequently again compounded, being pinnulated 

 with a third series of ramuli. Ramuli acute, transversely striate and subarticulate, 

 with hexagonal cells of nearly equal length and breadth. Antheridia oblong, 

 crowding round the tips of the ramuli. Stem and branches perfectly inarticulate, 

 areolated with polygonal cells of irregular shape and size. Colour., when dry, a 

 dark purplish brown. Substance rigid. It does not adhere to paper. 



Allied to R. complanata, but the surface cells are of larger size, and the ramuli 

 more evidently articulated. Indeed, except for the habit, which is that of a Ryti- 

 -phlcea, this plant might be placed in Polysiphonia. 



VII. DIGENIA. Ag. 



Frond filiform, rigidly horny, irregularly branched, inarticulate, densely cellular, 

 the surface cells minute ; branches densely clothed on all sides with rigid, hairlike, 

 subsimple, articulated, longitudinally striate ramuli. Coiiceptacles (unknown). 

 Tetraspores lodged in the swollen ramuli. 



The single species for which this genus has been set apart, though common in 

 the Mediterranean, the Red Sea, the Indian Ocean, and in the warmer parts of the 

 Atlantic, is still imperfectly known, its conceptacular fruit having hitherto escaped 

 notice. In assifning it a place among the Bhodomelece, the structure has alone 

 guided us ; the internal anatomy of the stem and branches being nearly similar to 

 that of the same parts in Phodomela ; while the ramuli are formed something on 

 the type of those of a Polysiphonia, or perhaps more nearly still on those of a 

 Bostrychia. The longitudinal stria? of the internodes do not consist of a single 

 elongated cell, as in Polysiphonia, but of a string of cells. 



