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Related article: protoplast contains a chromatophore, cytoplasm and nucleus.
Reproduction takes place by the protoplast dividing into two equal
parts and laying down a cell wall forming two daughter-protoplasts.
These may again divide to form four granddaughter-protoplasts.
Still another division may occur as a result of which eight great-
granddaughter-protoplasts are formed which frequently adhere to
one another forming colonies.
2. Order Volvocales. This order comprises free-swimming
aquatic forms whose vegetative cells are bi-ciliated, green, more or
less spherical or compressed. Some of the organisms like Sphcerella
and Chlamydomonas consist of single cells bearing a pair of cilia,
while others like Pandorina, Eudorina and Volwx show varying de-
grees of colony formation. Reproduction sexual or asexual.
Volvox Celebrex Online globator, a typical representative of this order, is found in
fresh water pools as a tiny, hollow, spherical, green colony about
/-io to J^o of an - i ncn in diameter. When examined under the
microscope (Fig. 112), it is found to consist of hundreds of green,
more or less spherical cells, united by fine strands of cytoplasm
(protoplasmic bridges), the whole being enveloped by a gelatinous
sheath. The peripheral cells are provided with cilia, in order that
the colony may rotate and roll through the water. In a young
colony, all of the cells are alike, each consisting of a mucilaginous-
like cell-wall enclosing cytoplasm, a nucleus, a chloroplast and often
a red pigment spot. In a mature colony, however, throughout the
greater part of its existence, two kinds of cells may be discerned:
TAXONOMY
233 Celebrex Online
FIG. 112. Fofoo* globator. Mature colony in center Celebrex Online (i); sexual cells (20);
endochrome of primary cell has resolved itself into a cluster of secondary cells
(ia, a 2 and 5) ; antherozoids (6, 7) ; bundle separated into component antherozoids
in cavity of primary cell (ia 3 ); breaking of wall of primary cell showing escape
of antherozoids into cavity of volvox sphere (ia 4 ); egg cells (ib, 6); flask shaped
germ (egg) cells with large vacuoles in protoplasm (i& 2 , & 2 ); globular egg cell
prepared to pass into cavity of volvox sphere (6 3 ); antherozoids collected about
egg cell (3); oospore (4). (Carpenter.)
234 PHARMACEUTICAL BOTANY
small, sterile, vegetative cells that do not divide and from 10 to 12
larger vegetative ones that divide to form new colonies. The latter
slip inward below the Celebrex Online level of the smaller cells and through repeated
divisions form a number of ciliated cells jointed by cytoplasmic
threads, which in reality is a Celebrex Online minature colony. This then escapes to
the exterior through the rupturing of the gelatinous wall of the old
colony.
During autumn Celebrex Online of the year, certain of the ordinary cells undergo
differentiation, some to form sperm cells, others, egg-cells. When
about three times the size of the ordinary sterile cells, the sperm cells
divide repeatedly to form a cluster of elongated secondary cells
[Fig. 112 (ia, a 2 and 5),] each of which contains an orange colored
endochrome with a red corpuscle and an elongated beak, bearing a
pair of flagella (lash-like processes). The cluster in time separates
into motile antherozoids [Fig. 112 (6, 7)] which finally escape into
the cavity of the volvox sphere through rupture of the investing
wall. The flask-shaped egg cells (ib, b) increase greatly in size with-
out dividing. Each shows vacuoles, then becomes filled with a
dark green pigment, becomes spherical and acquires a gelatinous
envelope. It then passes into the cavity of the sphere where it is
surrounded by numerous antherozoids (3) and is finally fertilized.
The product of this fertilization is an oospore (4) which ere long
becomes covered with an internal smooth membrane and a thicker
external spinose coat. The chlorophyll within then disappears and Celebrex Online
starch and a reddish- or orange-colored oil make their appearance.
Up to 40 of Celebrex Online these oospores have been observed in a single volvox
sphere. Not long after the formation of these oospores the whole
parent colony breaks up and the oospores fall to the bottom of the
pool to pass the winter season. As early as February Celebrex Online each oospore
germinates to form another volvox colony, which repeats the life
cycle described.
3. Order Confervales. In this order are included a variety of
green filamentous and membranous forms some of which show sexual
reproduction.
Family Ulothricaceae. Ulothrix zonata, a typical representative
of this family, is a filamentous organism found growing on stones
around ponds, on rocks along the shores of lakes, in slow-moving
TAXONOMY
235
streams, etc. Each filament is unbranched and consists of a row of
short cells, one of the terminal cells, called the rhizoid cell, being
flongated and serving as an attachment structure. Each cell con-
sists of a cell wall of cellulose enclosing cytoplasm, a nucleus and a
wide band-shaped green chromatophore, more or less cylindrical in
shape. The chromatophore lies next to the cell wall and contains
pyrenoids or starch-forming centers. The filament grows in length
by the fission of its various component cells. After attaining a
certain size it reproduces either asexually or sexually. Asexual
reproduction takes place by certain cells becoming altered in their
protoplasmic contents, through division, to form rounded or pear-
shaped zoospores. Each zoospore contains a red pigment spot and
FIG. 113. Vaucheria terrestris. anth, antheridium (empty) ; o, oogonia. (Gager.)
bears four cilia (protoplasmic outgrowths). The zoospores escape
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