IV. 
SPOROCHNACEiE. — Desmarestia. 
77 
cells, lengthening by division of the terminal cell, and becoming branched at 
intervals by the development of opposite budding cells from the shoulders of the 
older ones. Thus we have in its simplest form the type of the growth of the 
species ; namely, a repeatedly pinnate division, with opposite pinnules. These 
pinnated confervoid apices become gradually clothed with a stratum of minute 
cellules, which may be observed commencing to be formed on the lowermost cells 
(those nearest the compound portion of the branch), and gradually extending 
upwards. Thus at length the confervoid filament is completely enclosed in a 
cellular coating ; new coats are continually added to this ; — until the frond 
becomes a cylindrical, compound-cellular body, through the centre of which runs 
an articulated filament ; which filament was the earliest part formed, and the axial 
nucleus round which the other parts grew. 
The manner of growth in D. ligidata is precisely similar, except that in that 
species the new cellular integument to the primary filament is not developed 
equally on all sides, but extends chiefly laterally, so as to form at first a 
two-edged and then a flat or even leaf-like stem. In this process of lateral exten- 
sion, or widening of the stem, the lower portions of the pin me of the primary 
filament being enclosed within the cellular wings of the flattened branch, become 
the lateral nerves of the frond. Some of these merely reach the margin of the 
flat stem, or extend slightly beyond it, as a tooth, tipped with a pencil of fibres ; 
others, continuing to vegetate, become the nuclei of the young lateral branches. In 
the broad forms of D. ligulata , constituting J). herbacea of authors, the nervation 
and its origin are both very clearly seen. 
1. Desmarestia viridis , Lamour. frond cylindrical, filiform, repeatedly pinnate ; 
pinnae and pinnulae capillary, exactly opposite, patent. Kiltz. Sp. Alg. p. 570- 
Harv. Phyc. Brit. t. 312. Dichloria viridis , Grev. Alg. Brit. t. 6. J. Ag. Sp. Alg. 
vol. l,p. 164. Fucus viridis , FI. Dan. t. 886. Turn. IBist. t. 97. E.Bot. t. 1669- 
Hab. On rocks, stones, and the larger Algae in tide-pools, near low-water mark, 
and extending into deep water. Annual. Abundant on the shores of British 
America, and extending south to Boston Bay ; Cape Anne, Connecticut ; and 
Hell-gate, New York, Mr. J. Hooper. Unalaschka, Chamisso. (v. v.) 
Fronds from one to three feet in length, cylindrical, from a quarter line to half a 
line, or sometimes a line in diameter below, gradually attenuated upwards to a 
hairlike fineness, excessively branched, having an ovate outline when the branches 
are freely displayed. All the branches, and every one of the lesser divisions, 
down to the most minute ramulus, are exactly opposite and distichous ; the 
larger divisions are patent, or nearly horizontal, the lesser more erect. In a 
vegetating state the branches and ramuli terminate in extremely slender, 
articulated, byssoid filaments, which gradually become coated with cellules ; and 
then the imbedded filament becomes the axis of the compound frond. Structure 
densely cellular, with numerous large air-cavities dispersed through the cellular 
