IT. SPOROCHNACE^.— Desmaeestia. 77 



cells, lengthening by division of tte 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. Ugulata 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 pinna3 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. Ugulata, constituting D. herbacea of authors, the nervation 

 and its origin are both very clearly seen. 



1. Desmaeestia viridis, Lamour. frond cylindrical, filiform, repeatedly pinnate ; 

 pinnas and pinnulaj capillary, exactly opposite, patent. Kictz. Sp. Alg. p. 570- 

 Harv. Phyc. Brit. t. 312. Dichloria viridis^ Gh'ev. Alg. Brit. t. 6. J. Ag. Sp. Alg. 

 vol. l,p. 164. Fucus viridis, Fl. Dan. t. 886. Turn. Hist. t. 97. E. Bot. t. 1669- 



Hab. On rocks, stones, and the larger Algte 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 



