130 
SUPPLEMENT. 
Whether a distinct species or a mere variety of I. micans remains to be shewn, when 
some competent observer on the Pacific Coast shall have properly examined the several 
reputed species of this most troublesome genus. If we admit more than one species it 
is difficult to refuse admission to many, the forms are so varied. The present is, at 
least, a well-marked variety . 
Page 195, add, 
4. ILalosaccion dumontioides ; stem short, filiform, emitting many crowded, tubular, 
membranaceous, long branches, which are quite simple, destitute of ramenta, and taper 
much to the base and apex. 
Hab. Northumberland Sound, Queen’s Channel, lat. 76° N., Dr. Lyall. (v. s. in 
Herb. T.C.D.) 
Stem 1-3 inches long, simple or forked, filiform, about twice as thick as hog’s bristle, 
emitting throughout its length, and directed towards all sides, numerous crowded, perfectly 
simple branches. Branches two feet long, more than quarter inch wide in the middle, 
cylindrical for their greater extent, but attenuated and fusiform to the base, and tapering 
at the extremity to an acute point, hollow, destitute of 'ramenta, smooth and glossy, 
formed of a very thin membrane. Colour a brownish pinky-red, partly discharged in 
fresh water. Cellular structure very dense. 
I have some hesitation in proposing this as a species distinct from H. ramentaceum ; 
but if not a good species, it is at least a strongly marked variety, and has so much the 
external aspect of Dumontia jiliformis , that until I had submitted a section to the 
microscope, I supposed I had before me a very luxuriant specimen of that plant. The 
microscopic structure of the membrane is that proper to Halosaccion (section Haloccelia), 
but is not easy to see, as the collapsed cells do not readily expand on reimmersion of 
the dried frond. The substance is much softer and more membranous than in II. ra- 
mentaceum , and in drying the branches adhere much more strongly to paper. Dr. Lyall 
brought home several fine specimens. 
Page 242, add, 
16.* Callithamnion tenue ; filaments tufted, ultra-capillary, irregularly much 
branched, diffuse, flexuous, the branches and their divisions very generally secund, 
springing from the middle of the internodes; ramuli few and distant, patent, filiform, 
beset toward the attenuated apices with whorls of minute, byssoid fibres ; articulations 
cylindrical, those of the branches 4-6 times, those of the ramuli 3-4 times as long as 
broad, and gradually shorter towards the extremities, Griffithsia tenuis , Ay. Sp. Alg. 
p. 13. J. Ag. Sp. Alg. 2 , p. 84. Kiitz. Sp. Alg p. 661. 
Hab. Beesley’s Point, New Jersey, Mr. Samuel Ashmead. (v. s. in Herb. T.C.D.) 
Filaments 3-4 inches long, somewhat thicker than human hair, loosely tufted, 
flexuous, very irregularly branched, the ramification on a lateral, not a dichotomous 
