IV. 
FUCACEiE. 
49 
Order I.-FTJCACE M 
J. Ag. Sp. Alg., vol. 1, p. 180 ; C. Ag. Sgst. Alg. p. xxxvii, (in part) ; Encll. Gen. 
PL, Suppl. 3, page 29 (excl. gen.). Harv. Alan. Br. Alg., ed. 2, p. 11. FucoiDEiE, 
Grev. Alg. Brit. p. 1 ; Harv. Alan., ed. 1 , p. 1 . Fuce^e, Cystoseireas, Sargassete, 
and Halochlcge, Kiitz. Phyc. Gen., p. 349, et seq. Fucidas and Cystoseiridai, 
Lindl. Veg. King., p. 22. 
Diagnosis. Olive-coloured, inarticulate seaweeds, whose spores are contained in 
spherical cavities of the frond. (Plants of large size, tough , of leathery texture , 
becoming dark-coloured in drying .) 
Natural Character. Root almost always a conical holdfast, adhering by its 
base to rocks and stones, usually simple and undivided ; in a few instances sending 
off lateral creeping branches, and forming a mat, from which many upright fronds 
arise. 
Fronds of large size, inarticulate, leathery or rarely in parts thin and membrana- 
ceous ; tough, tearing with facility in a longtitudinal direction ; of an olive-broivn 
or olive-green colour, becoming foxy in age, and changing to a dark brown or black 
in drying ; composed of minute, coloured, or colourless cells arranged in filaments, 
and closely united together by a very firm intercellular substance. 
The habit is very various. In the least perfect genera (as Splachnidium) there is 
no distinction of stem, leaves, and organs of fructification, but the frond consists of a 
leathery bag, filled with loose jelly, through which a few longitudinal filaments 
pass. The spore- cavities are dispersed beneath the pores of the whole surface, and 
the frond is thus reduced to a root, and a universal receptacle of fructification. 
In others (Durvillcea, Sarcophycus) there is a stem which gradually expands at 
the summit into a leaf-like, cloven lamina, through which the spore- cavities are 
scattered ; these genera have the habit of Laminarioe, but the fructification of 
Fucaceae. 
In the next stage of development ( Myriodesma , Carpoglossum ,) the frond becomes 
more leaf-like, but the spore-cavities are still dispersed equally through all its 
divisions. 
To such forms succeeds Himanthalia , in which there is a clear distinction between 
the frond and the receptacle of fructification, but wherein the former is reduced to 
a cup-like air-vessel, while the latter is much branched and constitutes the bulk of 
the plant. In this case the true relations of the parts are determined by the 
VOL. HI. ART. 4. H 
