FUCACE.E. 49 



Order I.-FUCACEiE. 



J. Ag. Sp. Alg., vol. 1, p. 180 ; C. Ag. Syst. Alg. p. xxxvii, (injyart) ; Endl. Gen. 

 PL, Suppl. 3, page 29 (exd. gen.). Harv. Man. Br. Alg., ed. 2, p. 11. Fucoide^, 

 Grev. Alg. Brit. p. 1 ; Harv. Man., ed. 1, p. 1. FucEiE, Ctstoseire^, Sakgasse^, 

 and Halochlo^, Kiitz. Phyc. Gen., p. 349, et seq. Fucidje and CvsTOSEUiiD^, 

 L{7idl. Veg. King., p. 22. 



Diagnosis. Olive-coloured, inarticulcate 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 sendmg 

 oif lateral creei)ing 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-brown 

 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 fas 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 (Durvillasa, 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 Laminaria', but the fructification of 

 Fucacetp. 



In the next stage of development (Myriodesma, Carpoglossiim,) 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. ni. ART. 4. ^ 



