DASYCLADEiE. 
39 
thrice compounded and articulated ; being formed of two or three series of nearly 
cylindrical cells, four to six times longer than broad, filled with dark green slimy endo- 
chrome. The terminal cells are very obtuse. Fructification is formed at the axils of 
the ramelli, where two or three supplementary cells are developed and, become spherical 
sporangia , by absorbing all the endochrome of the cells from which they spring, 
and finally that of the whole frond. When ripe, these sporangia are membranous bags, 
stuffed with innumerable spherical spores. Colour , a deep grass-green. Substance , 
soft and somewhat gelatinous. 
This species closely resembles, in habit and structure, D. clavceformis of the Medi- 
terranean ; but the ramelli, even in the densest specimens, are much more distantly 
placed than in that plant, and the apices (or terminal cells) of all the American indi- 
viduals I have examined are perfectly blunt ; not mucronulate, as they are in JJ. clavce- 
formis. If this distinction prove constant, the species will be sufficiently characterised. 
Plate XLI. B. Fig. 1 . Dasycladus occidentalis ; the normal form. Fig. 2. An 
attenuated and depauperated variety ; both figures the natural size. Fig. 3. Trans- 
verse section of the frond, showing a whorl of trichotomous ramelli. Fig. 4. Portion 
of a fertile ramellus with sporangia. Fig. 5. A sporangium. Fig. 6. Spores from 
the same ; all the latter figures magnified. 
III. ACETABULABIA. Lamour. 
Root scutate. Frond stipitate, umbrella-shaped, thinly incrusted with calcareous 
matter. Stipes tubular, unicellular, cylindrical, when young emitting whorls of byssoid 
fibrills at and below the summit ; when mature, crowned with a peltate disc, formed of 
numerous radiating cuneiform cells. Cells of the disc at first containing granular 
endochrome, which is afterwards changed into spherical spores. 
The two species which are included in this genus are among the most elegant and 
singular of the Algae, resembling delicate fungi of the genus Agaricus , more nearly than 
any marine production. This is, however, descriptive only of the fully grown plant, 
for in the young state, the peltate umbrella which crowns the stipes is not found > In 
the youngest specimens which I have examined (represented at fig. 2 in our plate) 
the upper part of the stipe is beset at sub-distant intervals with whorls of extremely 
slender byssoid fibrills, above the last of which a young disc is commencing to be 
formed. In older plants these fibrills drop away, and their position is indicated by an 
annular row of holes, the tube being also swollen at each whorl, so as to appear jointed. 
There are no septa, however, and the tube is continuous, at least to the base of the 
young disc. When the disc is further advanced, a dense pencil of fibres springs from 
its centre, on its upper surface, or from what may be called its umbo, and which is 
