IV. 
FUCACEiE. — Fucus. 
67 
DOUBTFUL SPECIES. 
2. Cystoseira ( Pliyllacantha ) oligacantha , Kiitz. “ Of large size ; branches fili- 
form, bipinnate, slender ; pinnae very patent, alternate, sometimes opposite ; 
pinnules erecto-patent, sparingly spinous ; air-vessels chained, elliptic oblong ; 
receptacles nodoso-tuberculate, cuspidate.” Kiitz. Sp. Alg. p. 596. 
Hab. Newfoundland, Lenormand (fide Kiitzing). 
Possibly this may be a form of C. fibrosa ; but without seeing specimens it 
would be rash to decide. 
Y. FUCUS. L . (in part) Grev. 
Root a conical disc. Frond linear, compressed or flat, in the latter case tra- 
versed by a midrib, dichotomous, rarely pinnated : forming receptacles by trans- 
formations of the tips of the branches ; and vesicles (when present) by inflations 
in the substance of the stem or branch. Branches mostly fastigiate, in some species 
winged with lamina, in none having separate leaves. Air-vessels often absent, 
simple, innate in the branches. Receptacles terminal or lateral, oblong or ovate, 
filled with mucus through which a net-work of jointed filaments extends ; having 
numerous pores beneath which are placed the spherical conceptacles (or spore 
cavities). Spore-cavities generally diclinous, monoecious or mostly dioecious. 
Spores from two to eight in the same hyaline perispore, several such perispores 
rising from the walls of the cavity. Antheridia on branching filaments, ovoid, 
racemose or tufted. Paranemata simple, lining the cell. 
A genus of social plants occupying the space between tide-marks, and con- 
tributing, on the shores where they grow, fully three-fourths of the vegetable 
clothing of the tidal rocks. Almost all the species are natives of the Northern 
Hemisphere, and chiefly of the Atlantic basin, where there are seven species on the 
European and five on the American shore ; one of the latter being peculiar to 
America, and two of the former to Europe ; the rest common to both. One 
species, allied to F. nodosus , is found at the Cape of Good Hope. 
As already noticed in our Introduction, (p. 36), these common shore-plants 
yield, on incineration, a considerable per centage of carbonate of soda, to obtain 
which salt they were formerly largely collected and burnt. Iodine and. mannite 
are also among their secretions. 
By J. Agardh, in his recent work, this genus is divided into two, Fucodium and 
Fucus , the first of which, excluding some species, is identical with our first section. 
