having as yet obsened the act itself of their disjunction
from the membrane, it has not been ascertained whether it
was the cells themselves or that which they contain which
escaped from it. That which is certain is, that the sporules
of this plant are not more naked (an opinion advanced by
M. Gaillon) than those of any other Ulvacece.
“ The Ulvacece properly so called are composed of cells sometimes
arranged in a single layer, which constitutes an elongated
tube entirely empty, sometimes disposed in two layers, compressed
the one against the other, and forming a flat membrane
more or less extensive. Their sporules are lodged in
these cells, and issuing by a pore situated on the surface, they
offer the same phenomenon of locomotion which we have seen
to belong to the preceding families.
“ Their movement is more slow and in the cellules straighter
than amongst the Conferveoe. Their beak is not so pointed,
and is not near so well separated from the body ; but nevertheless
it is always the thinnest end of the oviform bodies
which is foremost during the movement. The sporules are
five or six in number in each cellule ; in some of them there
were two or three which were much smaller than the others,
a difference which is also observed in the Conferveoe, but in a
manner less apparent.
“ Finally, it is only in the Ulva clatlirata that I have observed
the complete developement of these sporules. The germination
(if one may so name a phenomenon analogous to that
act in more perfect plants) consists in this species of a longitudinal
expansion, during which the green matter insensibly
transforms itself into transverse bands. In this state one
might easily take the young plant for a species of Conferva,
but soon the bands being divided longitudinally, and so become
disposed in two series, one cannot longer mistake it.”
Section i.
Granules simply imbedded in the frond.
39. U L V A Linn.
Char. Frond gelatinous, saccate or membranaceous. Cells
scattered through the fro n d either singly, in pairs, or in
fours.
Name supposed to be from ul, water, in Celtic.
1. U lva bullosa Roth.
Plate L X X V I I I . Fig. 13.
Char. Frond very delicate, somewhat gelatinous, at fir s t saccate,
afterwards becoming expanded into a hroad waved
or torn floating membrane.
Eng. Bot. t. 2320.; Hook. Brit. Flor. vol. ii. p. 312.; Harv.
in Manual, p. 171.
Hab. In stagnant freshwater ponds and ditches.
Fronds clustered, at first fixed, afterwards floating, very thin
and gelatinous, of a pale green colour, becoming yellowish.
Cells in the fully developed plant single, and equally diffused
throughout the lamina. I f this disposition of the cells he not
constant, and if in the young condition of the frond they are
ever arranged in fours, as I believe to be the case, then I think
that this species can scarcely be regarded as distinct from
Tetraspora. lubrica. The size of the cells is the same in both.
2. U lva crispa lAght.
Plate L X X V I I I . Fig. 12.
Char. Fronds terrestrial, saccate, firm , densely tufted,
plaited and wrinkled, o f a roundish form. C,qW.s> arranged
in fours, crowded.
Ulva crispa Lightfoot. Grev. Alg. Brit. p. 175.; Hook.
Brit. Flor. vol. ii. p. 312.; Harvey, in Manual, p. 171.
Ulva furfuracea Horncastle. Grev. Crypt, t. 265.;
Hook. Brit. Flor. p. 312.; Harvey, in Manual, p. 171. ;
E. B. t. 2754.
Hab. On damp ground, rocks, thatched roofs, &c.; very
common, winter and spring ; rocks near the sea: Appin:
Captain Carmichael. On the walls of King’s College,
Cambridge: Rev. M. J. Bei'heley. Several places near