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I believe no botanist who has been accustomed to see Fu cus
ceranoides, and F. vesiculosus in a growing state, will
ever consider them as the same species. The total want of vesicles
in the former, its different substance, and permanently
distinct habit, seem to be completely satisfactory. Those persons,
too, who are in the habit of preserving both species, are
fully aware that F. ceranoides becomes perfectly dry under
pressure, in one-third of the time that is required to deprive
F. vesiculosus of its moisture. The alga now illustrated,
however we may be satisfied of the difference between the two
species above mentioned, is likely to puzzle the best naturalists,
being in some respects intermediate. In habit, thick coriaceous
substance, colour, vesicles, and large size, it agrees with
Fucus vesiculosus, but in the fructification it comes nearer to
F. ceranoides. In F. vesiculosus, the receptacles are situated
at the ends of the branches, singly or in pairs; and there is no
decided difference between the fertile and sterile branches. In
F. ceranoides, the receptacles are on the extremity of short, lateral,
repeatedly divided branches, each of these lateral branches
thus forming a sort of cyme; and it is worthy of notice, that
they are spreading, while the main terminal ones spring at a more
acute angle. In the plant now represented, the fructification
is also upon lateral branches, narrower than the main frond,
and equally forming a cyme, which, towards the lower part of
the frond, is sometimes of such a size as to produce fifty or sixty
receptacles; but it is very remarkable, that the lateral branches
here, are given off at an acute angle, like all those in the true
F. vesiculosus, unless when an axillary vesicle causes them to
spread. The frond is dotted with the same kind of minute
pores which produce tufts of white filaments in F. ceranoides
and vesiculosus.
This plant is so abundant in Bute, as in some places to exclude
almost every other.
Fig. 1. Summit o f a main branch o f F. vesiculosus, var. laterfructus, natural
size. Fig. 2. Section o f a receptacle. Fig. 3. Small portion o f a receptacle,
with a capsule and external ¡¡ore. Fig. 4. Seeds; magnified.
Figs. 5,-8. Receptacles ( f different forms, natural size.