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Related article: the bulb gives rise from its base to several slender elongated runners,
which, at their tips develop runner bulbs. These runner bulbs, the
third year, give origin to another set of runners similar to those
formed during the second Arcoxia 90mg year which also develop runner bulbs at
their tips. A foliage leaf is also formed by each. The following
spring (spring of fifth year) one of these bulbs develops into a
mature sporophyte plant, bearing a single flower at the summit of
its elongated scape. See Fig. 27.
RESEMBLANCES BETWEEN GYMNOSPERMS AND ANGIOSPERMS
1. In both are developed those structures in which there is no
homologue, e.g., flowers.
2. In both the flowers develop at least two sets of leaves (either
on one or two plants of the same species) called sporophylla or
sporophyll leaves, the stamens and carpels. The stamens or stam-
ina! leaves are also termed microsporophylls. The carpels or
carpellate leaves are also known as megasporophylls.
3. Both groups produce microspores or pollen grains and mega-
spores or embryo sacs.
4. In both are developed on the evident generation, the plant or
sporophyte and the gametophyte, the latter concealed within the
megaspore of the sporophyte.
5. Both develop seeds with one or two seed coats.
6. In both groups there is developed from the fertilized egg an
embryo which lies within the cavity of the megaspore.
7. In both there exists a root and a stem pericambium.
8. Both produce collateral vascular bundles. Very rarely do we
meet with concentric bundles in the stem or leaf of Angiosperms.
FUNDAMENTAL DIFFERENCES Arcoxia 90mg BETWEEN GYMNOSPERMS AND
i. The flowers of Gymnosperms are often monoecious or dioecious
but very rarely hermaphrodite, as in Welwitchia, whereas those of
Angiosperms are usually hermaphrodite, rather rarely monoecious,
still more rarely dioecious.
LIFE HISTORY OF AN ANGIOSPERM 59
2. In the Gymnosperms the sporophylls are usually inserted
either Arcoxia 90mg spirally or in whorls around a distinctly elongated axis,
whereas in Angiosperms the sprophylls are condensed to short
whorls or spirals set around a shortened axis, the floral axis or recep-
tacle, torus or thalamus, or, as in the more modified Angiosperms,
the floral axis may even become hollow.
3. In Gymnosperms the microsporophylls or stamens are usually
sessile, whereas in Angiosperms the microsporophylls are nearly
always stalked. Rarely do we find sessile anthers among Angio-
sperms, an instance of this being seen in Mistletoe (Viscum) where Arcoxia 90mg
the anthers are set on the staminal leaf.
4. In Gymnosperms there is a traceable prothallus or gametophyte
plant that later becomes the so-called "endosperm" of the gymno-
sperm, whereas in Angiosperms no recognizable prothallus has been
proven to exist.
5. The stored Arcoxia 90mg food tissue in Gymnosperm seeds is prothallial tis-
sue loaded with starch, etc., whereas in Angiosperm seeds the stored
food tissue (endosperm) is a special formation after fertilization.
6. Gymnosperms bear naked ovules and seeds while Angiosperms
bear covered ones.
7. In Gymnosperms there are distinct recognizable archegonia
formed on or imbedded in the prothallus, whereas in Angiosperms
there are no distinct archegonia, only an isolated egg or eggs.
8. In Gymnosperms there are not infrequently found several
embryos from one fertilized egg. This condition is called poly-
embryony. Polyembryony is unknown in Angiosperms, only a false
polyembryony being noticed.
9. In Gymnosperms the secondary xylem (wood) tissue of roots,
stems and leaves consists either of punctated or scalariform cells,
whereas in Angiosperms the secondary wood tissue may be varied
in structural aspect.
Vegetable Cytology treats of plant cells and their contents.
THE PLANT CELL AS THE FUNDAMENTAL UNIT
Schleiden, in 1838, showed the cell to be the unit of plant structure.
The bodies of all plants are composed of one or more of these funda-
mental units. Each cell consists of a mass of protoplasm which
may or may not have a cell wall surrounding it. While most plant
cells contain a nucleus and some contain a number of nuclei, the
cells of the blue-green algae and most of the bacteria have been found
to lack definitely organized structures of this kind but rather con-
tain chromatin within their protoplasm in a more or less diffuse
or loosely aggregated condition.
A TYPICAL PLANT CELL
If we peel off a portion of the thin colorless skin or epidermis from
the inner concave Arcoxia 90mg surface of an onion bulb scale, mount Arcoxia 90mg in water and
examine under the microscope, we find it to be composed of a large
number of similar cells which are separated from one another by
means of lines, the bounding cell walls. Under high power each of
these cells will exhibit the following characteristics:
An outer wall, highly refractile in nature and composed of cellulose;
which surrounds the living matter or protoplasm (See Fig. 29). This
wall is not living itself but is formed by the living matter of the cell.
Somewhere within the protoplasm will be noted a denser-looking
body. This is the nucleus. Within the nucleus will be seen Arcoxia 90mg one or
more smaller highly refractile and definitely circumscribed bodies,
the nucleolus Arcoxia 90mg or nucleoli. The protoplasm of the cell outside of the
nucleus is called the "cytoplasm." It will be seen to be clear and
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