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Related article: along the outer seed coat, Celebrex 200mg it is called the raphe.
MODE OF FORMATION OF DIFFERENT TYPES OF ALBUMEN Celebrex 200mg
If the egg-cell within the embryo sac segments and grows into the
embryo and, stretching, fills up the cavity without food material
laid down around it, it happens that the nutritive material lingers in
the cells of the nucellus, pressing around the embryo. This is called
Peris per mic albumen. Seen in the Polygonacea.
In by far the greater number of Angiosperms, the endosperm nu-
cleus, after double fertilization, divides and redivides, giving rise to
numerous nuclei imbedded in the protoplasm of the embryo sac, out-
side of the developing embryo. Gathering protoplasm about them-
selves and laying down cell walls they form the endosperm tissue
outside of the embryo. Into this tissue food is passed constituting
the Endospermic albumen.
In the Maranlacea, Piperacea, etc., nutritive material is passed Celebrex 200mg
into the nucellar cells causing them to swell up, while to one side a
small patch of endosperm tissue accommodates a moderate amount
PLANT ORGANS AND ORGANISMS 215
of nourishing substance, thus Celebrex 200mg resulting in the formation of abundant
perisperm and a small reduced endosperm.
Exalbuminous seeds are those in which the albumen is stored in the
embryo during the growth of the seed. Such seeds show the fleshy
embryo taking up all or nearly all the room within the seed coat.
Examples: Physostigma, Amygdala, etc.
Albuminous seeds are those in which the nourishment is not stored
in the embryo until germination takes place. Such seeds show a
larger nourishing tissue region and a smaller embryo region. Exam-
ples: Nux Vomica, Myristica, Linum, etc.
Gross Structure of a Monocotyl Seed (With fruit Celebrex 200mg wall attached),
Indian Corn. The ripened seed of Indian Corn is surrounded by a
thin, tough pericarp which is firmly adherent to and inseparable from
the Spermoderm or seed coat. Because of this fact, while in reality
a fruit called a caryopsis or grain, this structure is sometimes erro-
neously termed a seed.
The mature grain of most varieties of Indian Corn is flattened and
somewhat triangular in outline, the summit being broad and the
base comparatively narrow. The summit is indented and often
marked by a small point which represents a vestige of the style.
The basal or " tip" region marks the part of the grain which was in-
serted into the cob. Upon it maybe found papery chaff, represent-
ing parts of the pistillate spikelets. The groove noted on the
broader surface indicates the position of the embryo.
Histology Celebrex 200mg of the Indian Corn Seed (With fruit wall attached). If a
longitudinal section be cut through the lesser diameter of a soaked
grain, the following histologic characteristics will be observed:
1. The Pericarp or ripened ovarian wall which, alike Celebrex 200mg with all other
grains, adheres firmly to the wall of the seed forming a portion of
the skin of the grain. The pericarp comprises an outer epicarp of
elongated cells with thin cuticle, a mesocarp of thicker walled cells
without, becoming thinner within, and a layer of tube cells.
2. The Spermoderm or seed coat, a single layer of delicate elon-
3. The Perisperm, another layer directly underneath the Spermo-
derm, difficult to distinguish without special treatment, and repre-
senting the ripened nucellar tissue of the ovule.
2l6 PHARMACEUTICAL BOTANY
4. The Endosperm or nourishing tissue, consisting of: (a) The
Aleurone Layer, for the most part a single row of cells, containing
aleurone grains. Some of the cells may be seen to be divided by
tangential partitions, (b) Starch Parenchyma, consisting of two
regions: an outer horny zone composed of cells containing for the
most part polygonal starch grains and oil droplets; and an inner
mealy zone of cells with mostly rounded starch grains.
5. The Embryo, consisting of a single shield-shaped cotyledon
adjoining the endosperm, the plumule or rudimentary bud at the
end of the caulicle or rudimentary stem and the radicle or rudimen-
tary root, with its tip covered by a root cap. Continuous with the
root cap is a root sheath or coleorhiza. The cotyledon or seed leaf
consists of two parts : the scutellum which lies next to the endosperm,
and is an organ of absorption; and the sheafing portion which sur-
rounds and protects the rest of the embryo.
The embryo contains oil and proteids, but no starch.
If a similar longitudinal section of a soaked grain be mounted in
dilute iodine solution, the contents of the aleurone cells will be col-
ored yellow indicating their proteid nature, while the starch grains
will take on a blue to violet coloration. The endosperm will be
observed taking up most of the room within the seed Celebrex 200mg coat. The con-
tents of its cells are not baled Celebrex 200mg out to the embryo until after germina-
tion begins. Indian Corn is therefore an albuminous seed.
A MONOCOTYL SEEDLING
Germination. When any viable seed is planted in suitable soil,
and furnished with oxygen and water and a certain degree of heat,
germination takes place. In the presence of moisture, etc., the seed
swells, the ferments present within the cells of the endosper n then
change the insoluble proteid, starch, and oil to soluble materials,
which, in the case of Indian Corn, are absorbed in solution by the
scutellum which bales this nourishment out to other parts of the
growing embryo, there to be used in part in constructing new tissues,
and in part to be consumed fry oxidation or respiration. The process
of respiration or breathing takes place when the plant takes in oxy-
gen and gives off carbon dioxide. The oxygen oxidizes the tissues
PLANT ORGANS AND ORGANISMS 21 7
with an accompanying release of energy, which latter is necessary to
life and growth.
The combined pericarp and spermoderm bursts opposite the tip of
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