I if
f
»1
*
I,
♦
Monostroma W ittr o ck ii. Sorn. Notes Alg. p. 176.
Thallus membranaceous, gelatinous, bright green (18 mill.)
oblong, pedicellate, at first saccate, then open a t the summit,
margin becoming irregnlarly lobed. The adult plant becomes
sessile, and is attached by a part of its snrfaoe, when mature the
fronds are large (8 cent, diam.), the lobes plicate, elongated
and rounded, cell angular, subquaternate, in section of thallus
rounded, chlorophyllose body occupying about half the cell.
In salt or brackish water.
Perhaps hardly claiming a place in this work„ as it is more truly a
marine species.
Plate L I., fig. 8. Portion of a frond X 200. Pig. 9, 10, sections of
frond X 200. Pig, 11, zoogonidia X 300. Pig. 12, germinating X 200,
after Bornet.
Monostroma bullosum. W ittr. Mon,, p. 28, is the Tetraspora
bullosa of this work, se e jj. 16, plate vi., fig. 1.
F a m i ly II. SPH^ROPLBACB^.
Threads simple, with terminal vegetation, very long, articulate,
articulations cylindrical, by spurious septa multilocular.
Chlorophyllose mass distributed in annular bands, which enclose
from S-7 starch vesicles.
Propagation by oospores after sexual fecundation, very
numerous in the cells, at first green, then red, enclosed in a
stellate sporoderm.
Genus 57. S PH H IR O F L EA . Ag. (1824.)
Characters the same as given above for the family, which
consists but of one genus.
The following is an abstract of a memoir on Spliasroplea annulina, by
‘rk.“ f Nor. des Sci. Nat.,” 1856, p. 187), describing the process
oi tructification :—“ The structure of the resting-spores is very singular.
They are red spherical bodies, from one 120th to one 100th of a line in
diameter, and formed of two hyaline membranes, the interior of which
IS intimately connected with its plastic contents, whilst the exterior is
loose and elegantly plaited. These plaits or folds are so arranged that
they meet at their two poles ; often, however, they are very irregular
in shape and direction, especially in the larger spores.
“ In germination the resting-spores undergo several modifications. They
become granular and change to a dull brown red, and a more transparent
circle appears in their centre. Frequently the red matter changes to
green before the germination, and this charge of colour is gradual
proceeding from the circumference to the centre of tho cavity. At
length the whole of the plastic contents divides into two, then into four
or eight bodies, which burst the double envelope and disperse in the
water as so many zoospores.
“ The zoospores are of an elegant shape, but this is not more uniform
than their size or colour. Usually they are globular or shortly oylm-
drioal bodies, from one 190th to one 150th of a line long, of a beautitul
cinnabar or carmine red, and furnished at one of their ends with a small
colourless bead bearing two long cilia. Some of them are larger,
pyriform or fusiform, and the result probably of the undivided contents
of a resting-spore. Some of the zoospores are two-oolonred
—red towards the beak, and green throughout the other part, or
the two colours are variously disposed, the colourless bead or beak,
and the two cilia are invariably very distinct. The zoospores exhibit
a slow jerking movement daring several hours. This movement
is often interrupted for several hours, when the whirling suddenly
recommences. When the zoospores break through the integument
within which they are formed, they are not enveloped in cellulose but
already during their period of activity they begin to invest themselves
with a thin elastic pelliole. At the time of their geriniuation this
envelope thickens and lengthens in the form of a spindle, the two ends
soon tapering off into long tails, which even the enlarging body ot me
zoospore itself separates farther and farther apart. The contents of this
germ-oell, at first homogeneous and finally granular, change during this
first growth. What is left of the red oil is quickly transtormed into
chlorophyll, and the plantlet assumes a uniform green colour. Never-
theless one may perceive from the beginning a number of vacuoles, or
limpid, colourless droplets, in the midst of the protoplasm with which
they are filled, and between them the chlorophyll collects in rings more
or less distinot from each other. Soon large grains of starch appear in
these collections of green matter, so that the plantlet combines all the
characteristics of an adult cellule of the Sphairoplea, even before it has
exceeded a 13th of a line in length. The terminal tails have been
observed after the plantlet was more than half a line long Growth
takes place in the middle, by the suooessive division ot the older rings.
The contents of the adnlt threads presents the most beautiful appear,
anees. I t consists cf a colourless protoplasm, a green chlorophyll, a
watery liquid, and granules of sta rch ; the whole so disposed that the
liquid element forms large vacuoles in a row, like the pécaris ot a
necklet, and the diameter of which is nearly as great as that ot the thread
itself Often these vacuoles abut on each other, and seem to give birth
to partitions. In the spaces, between the pairs of vacuoles the green
plasma and grains of starch crowd together, though the space is disjointed
by the innumerable small vacuoles they throw oil.
“ On approaching fructification the vacuoles multiply to such an
extent as to give the endochrome the appearance of a frothy mass, in
which the starch granules are irregularly scattered. Soon atter the
starch granules assemble in pairs or threes or larger numbers, and
around these groups the green plasma becomes more plentiful, so that
in time they appear as so many equidistant cysts in the axis ot the
thread The greater part of the vacuoles having gradually disappeared,
the green clots assume a stellate appearance, connected by green
mncous rays or filaments. Between these star-like clots large vacuoles
are formed in pairs, which flatten so as to look like partitions, so that
each thread seems to be divided into numerous compartments.
“ The green matter contained in these compartments then undergoes
modifications, and the mucous rays are gradually resorbed, the ohloro.
phvll contracting meanwhile—sometimes to the right and sometimes to
the left In a short time the colourless plasm collects around the chlorophyll
in such a manner that the partitions disappear, and the whole
contents of the thread breaks up into a large number ot tree globular
masses, easily distinguished from the ambient colonrless mucilage, and
containing a certain quantity of irregularly distributed chlorophyll. These
i , i