112 ORD. LIV. Alge. _FUCUS VESICULOSUS. 
THE root of this plant is black and woody, forming an expanded callous 
disc ; the frond is smooth, glossy, flat, linear, winged, from one to four or 
five feet long, and from half an inch to two inches wide, forked near. the 
root, and afterwards repeatedly dichotomous, of a dark olive-green colour, 
becoming paler near the apices, and, when dry, black and dull. All the - 
branches are nearly of an equal height, with the apices rounded, often 
notched, with the margin entire. The substance of the frond is coriaceous, 
tough and flexible; (when dried brittle) and furnished with a midrib. In 
the membraneous part of the frond, throughout its whole length, are found 
immersed spherical vesicles, varying in size from that of a small pea to a 
hazel-nut, externally smooth, and containing in their cavity a quantity of 
air. The fructification consists of compressed, turgid receptacles, solitary or 
twin, placed at the end of the branches, varying in form, but mostly ellip- 
tical, from one-fourth of an inch to two inches Iong, and perforated with 
very minute pores, under which lie embedded spherical tubercles, composed 
of short jointed fibres, mixed with seeds of an elliptical form, surrounded 
with a pellucid limbus, and appearing under a powerful microscope, to con- 
tain six or seven roundish grains; the receptacle is filled with a tasteless 
and colourless mucus, through which passes anastomosing fibres. Its fruc- 
tification is produced in spring. Fig. (a) part of a receptacle magnified ; 
(6) horizontal section of a receptacle ; (c) longitudinal section of a vesicle ; 
(d) seeds ; (e) tubercle. 
The Fucus vesiculosus* is a perennial plant, growing abundantly on 
rocks and stones, or cast up on the beach every where on the British shores, 
and well-known by the popular name of sea-weed. In Scotland the name 
Wrack is applied to this and other species of Fuci which are gathered on 
the shores, for the manufacture of kelp.t+ When the plant is dried in the 
usual manner, it becomes brittle and of a dull blackish colour; and is often 
: : 
_ * The ancients were unacquainted with this plant, which was first. described by Clu- 
sius, under the name of Quercus marina.—Hist. i. 21. : 
+ Kelp is a very impure carbonate of soda, containing muriate and sulphate of soda, 
charcoal, and other impurities ; and is manufactured chiefly in Scotland, in the months 
of July and August. It is obtained by burning sea-weed in a kiln, until it becomes a 
compact mass, which, when cool is broken to pieces, and packed for use. Several kinds. 
of sea-weed are used for this purpose, but chiefly the Fucus vesiculosus, serratus, and 
