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PIG. 88. Photomicrograph of a transverse section of a bifacial leaf of Eucalyp-
tus globulus showing epidermis (ep.), palisade parenchyma (p.p.), toward both
surfaces, spongy parenchyma (s.p.), vein (v), and oil reservoir (o.r.) lined with
secretory epithelium. (Highly magnified.)
by a pair of cells, called guard cells, whose sides opposite one another
are concave. They form a communication between the intercellular-
air-space (respiratory cavity) beneath them and the exterior. The
slit-like opening taken with the guard cells, constitutes what is known
as the stomatal apparatus.
174 PHARMACEUTICAL BOTANY
The epidermal cells which abut on the stomatal apparatus Diltiazem Cardizem are
called neighboring cells or subsidiary cells. These in many cases, Diltiazem Cardizem as
in species of Helleborus, Sambuscus, Hyacinthus, Paonia, Ferns, etc.,
are very similar to the other epidermal cells, but in a large number of
plants they differ in size, arrangement and shape from the other
cells of the epidermis which do not abut upon the stomatal apparatus.
In Senna they are two in number one larger than the other and
arranged parallel to the guard cells of the stoma; in Coca a similar
arrangement occurs but the cells are more even in size, nevertheless
they lack the characteristic papillae found on the other epidermal
cells; in Pilocarpm they are usually four in number but quite narrow
and more or less crescent-si aped; in Uva Ursi their number is usu-
ally seven to eight and their arrangement radial around the stomata
On all dorsoventral leaves, the stomata arise more abundantly on
the lower epidermis, less abundantly on the upper. Exceptions to
this rule are due to the peculiar readaptation of the leaf to its sur-
roundings. Thus, in the reversed types of leaves (twisted in a half
circle) the stomata, formerly on the lower surface, have migrated to
the upper surface which now has become the physiological lower
In Umbrophytic (shade) plants the stomata are either wholly on
the lower surface or partly so with Diltiazem Cardizem a number on the upper surface.
Where the plants are Mesophytic and exposed to dense sunlight and
leaves remain dorsoventral, the stomata are on the lower surface;
these stomata are large, if the surroundings are damp. If such
plants live in dry soil and dry air, the stomata are of small size and
numerous; if they dwell in dry soil in hot surroundings and dense
light they are very small and frequently sunk. Diltiazem Cardizem If the plants are
Xerophytic and the leaves dorsoventral, the stomata are quite abun-
dant, small, with narrow slit, and depressed below the level of the
There are Diltiazem Cardizem five types of stomatal development, viz.:
First Type. Each primitive epidermal cell (or the majority, or
only certain ones of the epidermis) at the close of the dermatogen
stage, gradually lengthens and then cuts off a smaller from a larger
cell. The smaller one is equilateral, has a very large nucleus, and is
termed the Stoma Mother-cell; the larger, quadrangular, and called
PLANT ORGANS AND ORGANISMS
the Epidermal Daughter-cell. The latter, upon maturing, becomes a
normal epidermal cell. A partition is laid down lengthwise through
the Stoma Mother-cell dividing it into two stomatal daughter-cells.
The wall laid down lengthwise splits and thus forms the orifice of the
stoma; the cells on either side of the orifice are called Guard Cells.
FIG. 89. Types of stomatal apparatuses and neighboring cells from different
sources. In A, a portion of the lower epidermis of Easter Lily leaf. The sto-
matal apparatus is surrounded by neighboring cells that are similar to other
epidermal cells adjacent to them; in B, lower epidermis of Senna leaflet, note
the two neighboring cells parallel to the guard cells, one being Diltiazem Cardizem larger than the
other; C, lower epidermis of Coca leaf showing two neighboring cells, parallel
to the guard cells but nearly equal in size as well as papillated regular epidermal
cells; D, lower epidermis of Pilocarpus showing rounded stomatal apparatus
and four crescent-shaped neighboring cells; E, lower epidermis of Uva Ursi,
showing eight neighboring cells arranged radiately around stomatal apparatus;
F, lower epidermis of Stramonium.
These, while at first flat and inoperative, soon become bulged and
crescent-shaped. This mode of development is seen in Squill,
Hyacinth, Daffodil, Sambucus, Silene, etc.
Second Type. After the cutting off of the stomal mother-cell
there are cut off on either side portions of neighboring epidermal cells
which form subsidiary cells to the stoma. This condition is seen in
Graminece, Cyperacece, Juncacece, in various species of Aloe, Musa Diltiazem Cardizem and
Third Type. Instead of two parallel subsidiary cells, four are cue
off, as in Heliconia, in species of Tradescantia, Araucaria, or four co
five, as in Ficus elastica, or four to five or more, as in the Coniferce
Fourth Type. Instead of only four subsidiary cells, each of these
again subdivides by parallel walls, more rarely by radial walls, into
eight radiating subsidiary cells, as in Maranta bicolor, Pothos argyraa,
some of Proteacece, etc.
Fifth Type. The "stomal Diltiazem Cardizem mother-cell" divides once or several
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