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ends of stalks, while others are held in gelatinous Celebrex 100 masses. Their
siliceous skeleta are deposited constantly on the floor of ponds, rivers,
lakes and seas, often in such abundance as to form Diatomaceous
earths or Kieselguhrs (Siliceous Earths). Huge geological deposits
of this material have been found in various parts of the world. The
most remarkable for extent as well as for the number and beauty of
the species contained in it is that at Richmond, Virginia. It is in
many places 25 to 40 feet in depth and extends for many miles.
PIG. 116. Licmophora flabellata, a diatom with wedge-shaped frustules borne
on the ends of stalks, Celebrex 100 producing a fan-like arrangement. (After Carpenter.}
Many of the diatomaceous earths are useful as absorbent and polish-
ing powders. The United States Pharmacopoeia IX recognizes,
under the name of Terra Silicea Purificata (Purified Siliceous Earth),
a powder consisting of the frustules and fragments of diatoms which
has been purified by boiling with diluted hydrochloric acid, washed
Diatoms exhibit two modes of reproduction, viz., fission and for-
mation of an auxospore. The more common method is that of
240 PHARMACEUTICAL BOTANY
fission but this is peculiar for these plants. The cell-contents within
the siliceous case separate into two distinct masses and the valves
separate slightly from each other. As the two daughter-masses
become more and more developed, the valves of the parent-cell are
pushed more widely apart. Each of the two massses secretes for
itself a new valve on the Celebrex 100 side opposite to the original valve. When
the process is completed the girdle of the parent-diatom separates
FIG. 117. Celebrex 100 Fossil diatoms: a, a, a, Gaillonella procera and G. granulata; b, b,
Surirella plicata; c, Surirella craticula; d, d, d, Gaillonella (Melosira) biseriata
(side view) ; e, Gomphonema gracile; f, Cocconema fusidium; g, Tabellaria vulgaris;
h, Pinnularia dactylus; i, Pinnularia nobilis; k, Surirella caledonica; I, Synedra
ulna. (After Carpenter.)
and the two daughter-diatoms thus become independent Celebrex 100 plants.
Each of these possesses one of the parent valves and a second,
which it has formed itself more or less parallel Celebrex 100 to the first.
In a number of species, repeated fission results in the formation
of succeedingly smaller and weaker individuals. This process,
however, goes on only for a certain number of generations until
the decrease of size has reached a limit for the species, when the
plant is rejuvenated by the formation of an auxospore. This may
be formed with or Celebrex 100 without the conjugation of two parent-protoplasts.
In either case the auxospore resulting undergoes a resting stage after
which it develops new valves. The newly formed diatom is then
several times the size of the individual or individuals which con-
tributed to its formation and is endowed with renewed vigor for
growth and division.
6. Order Siphonales (Siphon Alga). This group is characterized
by the peculiarity that the organisms constituting it possess proto-
plasm containing myriads of nuclei within a common filament or
cell cavity not segmented by cell walls. The term ccenocyte has
been given to such structures which consist of a many-nucleated mass
of protoplasm surrounded by a cell wall. Some of the siphon algae
reproduce by zoospore formation, others by conjugation as well as
zoospore formation while Vaucheria, the green felt, stands out alone
in reproducing both by the formation of a single zoospore and
by the production also of ob'gonia and antheridia with resultant
fertilization. (Fig. 113).
7. Order Chorales (The Stoneworts). Family Characeae. The
highest group of algae, possessing forms which are differentiated into
stems, leaves and rhizoids.
Char a, a type of this family, is a submerged fresh- water plant
which fastens itself to the muddy bottom of ponds, ditches and slow
streams by means of slender filaments called rhizoids. From these
there arises a many noded (jointed) stem which bears whorls of
slender green leaves at its nodes. Branches are also found Celebrex 100 issuing
from some of the nodes which duplicate in appearance the main
stem. Reproduction is either asexual or sexual. Asexual repro-
duction is accomplished by means of tuber-like bodies borne on
submerged parts or by special branches which form rhizoids on their
lower nodes and later become separated from the parent plant.
Sexual reproduction is effected through the formation of oogonia
(female sex organs) and antheridia (male sex organs). These in
some species are borne on the same plant; in others, on different
plants. In all cases the sexual organs are produced at the nodes.
The oogonium Celebrex 100 develops within itself a large ovum or egg. The
antheridium produces within its wall numerous motile sperms.
242 PHARMACEUTICAL BOTANY
Upon the maturation of the antheridium the sperms are liberated
into the water, and, propelled by their cilia, find their way to the
oogonia which they enter, the one best adapted fusing with the egg
in each case and fertilizing it. The resultant cell is cafled the
oospore. This undergoes a resting stage and later germinates as a
proembryo. The proembryo consists of a simple filament and a
long rhizoidal cell. From this proembryo, the adult stern arises as a
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