are larger.
=Cambium.= The cambium cells are rectangular in shape; the walls are
thin and white.
=Xylem.= The xylem is composed of tracheids, wood parenchyma, and
wood fibres.
=Tracheids.= The tracheids are the largest diameter cells of the
centre of the root. The walls are thick and the cells are slightly
angled in outline.
=Wood Parenchyma.= The wood parenchyma cells surrounding the
tracheids are five to seven, angled, and the walls are not so thick
as the walls of the tracheids.
=Medullary Rays.= The medullary ray cells resemble the structure of
the wood parenchyma cells, but they are radially elongated.
=Pith Parenchyma.= The cells forming the pith parenchyma are larger
than the cells of wood parenchyma, but their structure is similar.
CROSS-SECTION RUELLIA ROOT
The cross-section of ruellia root (Plate 90) shows the following
structure. It should be carefully noted how the structure differs
from that of pink root:
=Epidermis.= The epidermal cells are angled and variable in size;
many of the epidermal cells are modified as root hairs.
=Hypodermis.= The cells of the hypodermis are one layer in thickness
and their structure is similar to the epidermal cells.
=Cortex.= The cortex contains parenchyma and stone cells. The outer
layers of the cortical parenchyma cells are round in outline, and
they contain dark-brown cell contents, while the cortical parenchyma
cells bordering on the endodermis are small and they are free of
dark-brown contents.
Many of the inner parenchyma cells contain amorphous deposits of
calcium carbonate.
[Illustration: PLATE 90
RUELLIA ROOT (_Ruellia ciliosa_, Pursh.).
1. Epidermis with root hair. 2. Parenchyma cells with dark
contents. 3. Sclerid. 4. Parenchyma without dark cell contents. 5.
Endodermis. 6. Bast fibers and phloem. 7. Cambium. 8. Xylem. 10.
Pith.]
The =stone cells= are porous and striated, and the walls are thick
and white.
=Endodermis.= The endodermal cells are tangentially elongated, and
the walls are thin and white.
=Pericycle.= The cells forming the pericycle are the sieve cells,
bast fibres, and phloem parenchyma.
The =sieve cells= are small, angled cells with thin, white walls.
The =phloem parenchyma= cells resemble the sieve cells, but they are
larger.
The =bast fibres= occur singly or in groups of two or three. They
are rounded in outline, and the walls are white, non-porous, and
non-striated.
=Xylem.= The xylem is composed of vessels, wood parenchyma, and wood
fibres.
=Vessels.= The vessels are rounded in outline and few in number.
=Wood Parenchyma.= The wood parenchyma cells are variable in size and
shape, but all the cells are angled in outline.
=Medullary Rays.= The medullary ray cells are not clearly
distinguishable.
=Pith Parenchyma.= The pith parenchyma cells of the centre of the
root resemble the cortical parenchyma cells.
That the structure of rhizomes is similar to the structure of roots
is shown by the drawings of spigelia rhizome (Plate 91), and by
ruellia rhizome (Plate 92).
CROSS-SECTION SPIGELIA RHIZOME
The cross-section of spigelia rhizome (Plate 91) is as follows:
=Epidermis.= The epidermal cells are nearly angled and free of cell
contents.
=Cortex.= The cortical parenchyma cells are usually slightly
tangentially elongated. The cells of the outer layers are larger than
the cells of the inner layers.
=Phloem.= The phloem contains sieve cells and phloem parenchyma. The
sieve cells are small, angled cells with thin, white walls.
The phloem parenchyma cells resemble the sieve cells, but they are
larger.
[Illustration: PLATE 91
CROSS-SECTION OF RHIZOME OF SPIGELIA MARYLANDICA, L.
1. Epidermis. 2. Cortical parenchyma. 3. Phloem. 4. Cambium. 5.
Xylem. 6. Internal phloem. 7. Pith with starch.]
[Illustration: PLATE 92
CROSS-SECTION OF RHIZOME OF RUELLIA CILIOSA, Pursh.
1. Epidermis. 2. Cystolith. 3. Stone cell. 4. Cortical parenchyma.
5. Bast fibres. 6. Pericycle. 7. Xylem. 8. Pith.]
=Cambium.= The cambium cells are rectangular, and they are usually
not clearly seen because the walls are partially collapsed.
=Xylem.= The xylem is composed of vessels, wood parenchyma, medullary
rays, and pith parenchyma.
=Vessels.= The vessels are slightly angled in outline and few in
number.
=Wood Parenchyma.= The wood parenchyma cells are small and angled.
=Medullary Rays.= The medullary ray cells are tangentially elongated,
but in structure resemble the wood parenchyma cells.
=Pith Parenchyma.= The pith parenchyma cells are rounded in outline
and contain small, simple, rounded starch grains.
CROSS-SECTION RUELLIA RHIZOME
The cross-section of ruellia rhizome (Plate 92) differs from the
structure of spigelia rhizome. It is as follows:
=Epidermis.= The epidermal cells vary in shape from nearly square to
oblong, and they are filled with dark-brown cell contents.
=Cortex.= The cortex contains parenchyma and stone cells.
The outer layer of the cortical parenchyma cells are variable in size
and many of the cells contain deposits of calcium carbonate and dark
cell contents; the inner parenchyma cells are larger and they are
free of the dark-brown cell contents, but many of the cells contain
deposits of calcium carbonate.
Stone cells with thick, white, porous, and striated walls occur in
among the cortical parenchyma cells.
=Phloem.= The phloem contains sieve cells, phloem, parenchyma, and
bast fibres.
The =sieve cells= are small and with thin, white, angled walls.
The =phloem parenchyma= cells resemble the sieve cells, but they are
larger.
The =bast fibres= occur singly or in groups of two or three. The
walls are white, non-porous, and non-striated.
=Cambium.= The cambium layer is composed of rectangularly shaped
cells, which are frequently obliterated.
=Xylem.= The xylem contains vessels, wood parenchyma, and medullary
rays.
The =vessels= are large, rounded cells with thick walls.
The wood parenchyma consists of thick-walled cells of irregular size
and form.
The =medullary rays= are tangentially elongated and rectangular in
form.
=Pith parenchyma.= The pith parenchyma cells are rounded in outline
and as large as the cortical parenchyma cells.
POWDERED PINK ROOT
When the roots and rhizomes of spigelia are powdered (Plate 93) they
show the following structure:
The epidermal cells are small and brownish on surface view, varying
in size from 13 by 18 micromillimeters to 31 by 40 micromillimeters.
When associated with parenchyma they appear as black masses. The
cortical parenchyma cells are rounded and vary in size from 23 by
26 micromillimeters to 37.5 by 90 micromillimeters. Many of the
cells from the root contain larger quantities of minute single
rounded starch grains varying in size from 1 micromillimeter to 4
micromillimeters. The larger round single starch grains are found in
both the cortical and pith parenchyma of the rhizome. They vary in
size from 5 micromillimeters to 18 micromillimeters. The conducting
elements are pitted tracheids varying from 10 micromillimeters to 38
micromillimeters in diameter. A few pitted and annular vessels are
also found. The only fibres occurring are found in the xylem. They
are not a prominent feature of the powder, as their walls break up
into minute fragments. The pith parenchyma varies in size from 13 by
19 micromillimeters to 75 by 82.5 micromillimeters. It is in these
cells that the largest starch grains occur.
Distinguishing diagnostic characters of the powder:
1. Parenchyma with starch.
2. Dark masses of epidermal tissue.
3. Spigelia should contain starch, and it should not contain
cystoliths, stone cells, or long, white-walled bast fibres.
POWDERED RUELLIA ROOT
When the roots of ruellia root and rhizome are powdered (Plate 94)
they show the following structure:
[Illustration: PLATE 93
POWDERED SPIGELIA MARYLANDICA, L.
1. Epidermis and cortical parenchyma. 2. Tracheids and fibres. 3.
Parenchyma cells of the root containing the small starch grains,
longitudinal view. 4. Parenchyma of the rhizome containing the
large starch grams, transverse view. 5. Tracheids. 6. Surface view
of the epidermal cells. 7. Starch scattered through the field. 8
and 8´. Dark masses of epidermal and underlying tissue.]
[Illustration: PLATE 94
POWDERED RUELLIA CILIOSA, Pursh.
1. Short, broad cystoliths from the rhizome, 1´. Long cystoliths
from the root. 2 and 2´. Long, narrow, white-walled bast fibres. 3.
Tracheal tissue from the xylem of the stem. 4. Root parenchyma. 5.
Tracheal tissue from the xylem of the root. 6. Cortical parenchyma
cells from the rhizome with short, broad cystoliths. 7 and 7´.
Long, thick-walled sclerids from the root. 8. Short, broad sclerids
from the stem. 9. Pitted pith parenchyma from the stem with
intercellular space. 10. Parenchyma of the root with sclerid and
cystolith, longitudinal view.]
The epidermal cells vary from 7.8 by 15.6 micromillimeters to 15.1
by 16.6 micromillimeters. The cell contents are dark and the walls
are light. A few rows of the outer cortical parenchyma cells of both
the rhizome and the root have dark cell contents and white walls. The
dark contents disappear toward the phloem. The cortical cells vary
from 13.6 by 14.3 micromillimeters to 89.5 by 90.9 micromillimeters.
In the cortical parenchyma cells of the rhizome are found the short,
broad cystoliths measuring up to 52 by 62 micromillimeters. In the
corresponding cells of the root are found the long, narrow cystoliths
which measure up to 68.4 by 187.2 micromillimeters. Scattered
throughout the powder are seen three distinct types of sclerids
(stone cells) which are associated with the cortical parenchyma of
both the stem and the root. Most of them are found, however, in
the roots. First, the short, broad stone cells from the stem basis
have square ends; the walls vary from 13 to 19.5 micromillimeters
in thickness with branching pores which extend toward the adjacent
cell. These sclerids vary in size from 52 by 54.6 micromillimeters
to 45 by 130 micromillimeters. Secondly, the long stone cells from
the root vary from 32 by 96 micromillimeters to 45.5 by 542.5
micromillimeters with walls 16 micromillimeters thick. The width of
the cell and the thickness of the wall vary but little throughout
their entire length. The third type of stone cell also from the root
has unequally thickened walls and the ends are square or blunt. A few
long, narrow, colorless, thin-walled bast fibres also occur. They
are 13 micromillimeters wide, with walls 3.9 micromillimeters thick.
Annular spiral and pitted vessels are also found scattered throughout
the powder.
The diagnostic characters of the powder are:
1. The short, broad, and long, narrow cystoliths.
2. The short, broad, and long, narrow sclerids.
3. The long, narrow, thin, white-walled bast fibres.
In poke root, ipecac, sarsaparilla, and veratrum are raphides. In
belladonna and horse-nettle roots are micro-crystals. In calumba,
stillingea, krameria, licorice, scamony root are prisms. In
saponaria, jalap, althea, spikenard, rumex, rhubarb are rosette
crystals. In pleurisy roots both prisms and rosettes occur.
In gentian, senega, symphytuns, lovage, parsley, inula, echinacea,
angelica, burdock, and chicory no crystals of any kind occur. Root
hairs occur in cross-sections of sarsaparilla root and false unicorn,
but with these exceptions: root hairs do not occur on roots, because
the younger part of the root with root hairs is not removed from
the soil when the drug is collected. In sarsaparilla root there
are several layers of hypodermal cells; in most roots there are no
hypodermal cells. In the non-woody roots or the roots of herbs the
parenchyma cells form the greater part of the tissues of the root.
In ruellia root are stone cells; in spigelia root and many other
roots there are no stone cells. In ruellia root are bast fibres; in
spigelia, gentian, ipecac, chicory, dandelion, symphytum, and lovage
no bast fibres occur. In all the woody roots there is a periderm
consisting of typical cork cells, as in black haw; or stone cells, as
in asclepias; or of a mixture of lifeless parenchyma, medullary rays,
etc., as in Oregon grape root.
Woody roots have a phellogen layer which is absent in the non-woody
roots.
The numbers of layers of cortical parenchyma differ in the same
root according to its age, but for a given root there is a normal
variation.
The number of layers of cortical parenchyma in proportion to other
cells is less in woody roots.
In woody roots there is no endodermis. The cambium in these
cases shows clearly between the phloem and the xylem part of the
fibro-vascular bundle.
In woody roots the wood fibres are well developed and form a large
part of the root, and the medullary rays have pitted side and end
walls.
The description given above of ruellia root is not typical of all
roots, but the structure represents the greater number of the
elements that it is possible to find in a root. In many roots, for
instance, there are no stone cells, in others no epidermis and no
endodermis. In asclepias, aconite, and calumba stone cells occur.
In symphytum, chicory, dandelion, burdock, elecampane, pyre thrum,
gentian, and senega no stone cells occur. In aconite, althea,
asclepias, belladonna, bryonia, columba, ipecac, jalap, krameria,
sarsaparilla, scamony, stillingea, and rumex are characteristic
starch grains. Symphytum, chicory, dandelion, burdock, elecampane,
and pyrethrum contain inulin, but no starch. In saponaria, gentian,
and senega neither starch nor inulin occurs.
When studying roots the nature of the epidermis or the periderm must
be considered, as also the number of layers of cortical parenchyma;
the occurrence, distribution, and amount of stone cells when present;
the presence or absence of the endodermis; the occurrence and
structure of bast fibres when present; the nature of the cambium
cells; the width and structure of the medullary rays, the size of the
wood fibres and wood parenchyma, and the nature of the cell contents
and the arrangement of the fibro-vascular bundle.
CHAPTER II
STEMS
When studying stems it should first be determined whether they were
derived from monocotyledonous or dicotyledonous plants. This fact is
ascertained by determining the type of the fibro-vascular bundle. See
Chapter XI. The next fact to determine is whether the stem is from an
herb or from a woody plant. This fact is readily determined because
herbaceous stems have a true epidermis, masses of collenchyma at
the angles of the stem. The cortical cells contain chlorophyll, and
the pith is very large. Woody stems have a corky layer, a phellogen
layer, and the pith is very small except in the very young woody
stems.
Having determined these facts, a study should be made of the
arrangement, form, structure, color, and the cell contents of the
different cells in order to determine the species of plant from which
the stem was obtained.
HERBACEOUS STEMS
The great variation in the structure of herbaceous stems is shown
in the cross-sections of spigelia (Plate 95); in ruellia (Plate
96); in the charts of powdered genuine horehound, powdered spurious
horehound, and in the chart of powdered insect flower stems.
CROSS-SECTION SPIGELIA STEM
Spigelia stem (Plate 95) has the following characteristic structure:
=Epidermis.= The epidermal cells are papillate.
=Cortex.= The cortical parenchyma cells consist of tangentially
elongated cells which are oval in outline.
=Phloem.= The phloem consists of sieve cells, phloem parenchyma, and
of bast fibres.
[Illustration: PLATE 95
CROSS-SECTION OF STEM OF SPIGELIA MARYLANDICA, L.
1. Papillate epidermis. 4. Phloem. 7. Inner phloem.
2. Cortical parenchyma. 5. Cambium. 8. Pith.
3. Bast stereome. 6. Xylem.]
The =sieve cells= are small, and with thin, white, angled walls.
The =phloem parenchyma= resembles the sieve cells, but they are
larger.
The bast fibres are rounded in outline and the walls are thick,
white, non-porous, and non-striated.
=Cambium.= The cambium cells are rectangular in shape or the walls
are collapsed and the cells indistinct.
=Xylem.= The xylem contains vessels, wood parenchyma, medullary rays.
The vessels are small and angled, the walls are thick and white.
=Wood parenchyma.= The cells are variable in size and shape, and
the walls are thick. The medullary ray cells are small, narrow, and
tangentially elongated.
=Internal Phloem.= External to the pith parenchyma are isolated
groups of internal phloem consisting of sieve cells.
=Pith Parenchyma.= The pith parenchyma cells are oval in form and
irregularly placed. The cells contain small, simple starch grains.
RUELLIA STEM
The cross-section of ruellia stem (Plate 96) is as follows:
=Epidermis.= The epidermal cells are variable in shape and very
large. There are no cell contents.
=Cortex.= The cortex consists of collenchyma and parenchyma cells and
stone cells.
The =collenchyma cells= have very small, angled cavities and very
thick walls. These cells make up the greater part of the cortex.
The =cortical parenchyma= cells are variable in size and shape. The
stone cells occur singly or in groups. The walls are thick, white,
porous, and striated, and the central cavity is frequently quite
large.
=Phloem.= The phloem contains sieve cells, phloem parenchyma, and
bast fibres.
The =sieve cells= have thin, white, angled walls.
The =phloem parenchyma= cells are frequently tangentially elongated,
otherwise they resemble the sieve cells.
The =bast fibres= occur alone or in groups. The walls are thick,
white and porous.
[Illustration: PLATE 96
CROSS-SECTION OF STEM OF RUELLIA CILIOSA, Pursh.
1. Epidermis. 2. Collenchyma. 3. Parenchyma. 4. Sclerids. 5. Bast
fibres. 6. Phloem. 7. Cambium cells. 8. Xylem. 10. Pith parenchyma.]
=Cambium.= The cambium cells are rectangular in shape and the walls
are thin.
=Xylem.= The xylem contains vessels, wood parenchyma, and medullary
rays.
The =vessels= are large; the walls are thick, white, and angled.
The =wood parenchyma= cells are variable in size and shape and the
walls are angled.
The =medullary ray cells= are radially elongated and rectangular in
shape.
=Pith Parenchyma.= The pith parenchyma cells are large and rounded in
shape.
POWDERED HOREHOUND
The structure of powdered horehound is shown in Chart 97. The
epidermal cells of the leaf (1) are wavy in outline, the guard cells
are elliptical, the stoma lens-shaped, the epidermis often showing
hairy outgrowth as in the illustration. The epidermal cells of the
petals (2) have irregularly thickened beaded walls. The non-glandular
hairs from the calyx (3); the long, thin-walled, multicellular
non-glandular twisted hairs (4) from the leaves and stems; long,
thin-walled, unicellular hairs (5) from the tube of the corolla; the
glandular hairs (6) with a one-celled stalk and with two secreting
cells divided by vertical walls; the eight-celled glandular hair
(7) as seen in surface and side view; the spiral and reticulated
conducting cells (8); the thick, white-walled fibres from the stem
(9); the pollen grains (10) with nearly smooth walls.
The diagnostic elements of the U. S. P. horehound are the long,
twisted, multicellular hairs (4), the glandular hairs (7), and the
pollen grains (10).
POWDERED SPURIOUS HOREHOUND
Marrubium peregrinum, which is a related species of horehound
and which is a common adulterant of horehound, has the following
structure (Plate 98):
[Illustration: PLATE 97
POWDERED HOREHOUND (_Marrubium vulgare_, L).
1. Epidermis of leaf showing the wavy epidermal cells, stoma,
and a clustered hair. 2. Surface view of the petal epidermis. 3.
Non-glandular hair from the calyx or corolla. 4. Long, thin-walled,
twisted, non-glandular hairs from the leaves and stem. 5.
Unicellular non-glandular hair from the tube of the corolla. 6.
Glandular hairs with a one-celled stalk and with two secreting
cells divided by vertical walls. 7. Surface and side view of the
eight-celled glandular hairs. 8. Conducting cells. 9. Fibres from
the stem. 10. Pollen grains.]
[Illustration: PLATE 98
SPURIOUS HOREHOUND (_Marrubium peregrinum_, L.)
1. Surface view of the leaf epidermis. 2. View of the petal
epidermis. 3. Non-glandular multicellular branched hair from
the stem, leaves, or flowers with a few of the lower branches
broken. 4. Broken pieces and branches from the compound hairs
scattered throughout the field. 5. Unicellular glandular hair
with a two-celled stalk. 6. Under-surface view of an eight-celled
glandular hair. 7. Side view of eight-celled glandular hair. 8.
Long, pointed, unicellular, non-glandular hair from the corolla,
the wall irregularly thickened near the apex. 9. Fibres. 10. Pollen
grains, 11. Conducting cells of leaf.]
[Illustration: PLATE 99
POWDERED INSECT FLOWER STEMS (_Chrysanthemum cinerariifolium_,
[Trev.], Vis.)
1. Surface view of epidermis.
2. Cross-section of epidermis.
3. Hairs.
4. Fibres.
5. Cross-section of fibres.
6. Longitudinal view of pith parenchyma.
7. Cross-section of pith parenchyma.
8. Conducting cells.]
The wavy leaf epidermis (1) with stoma; the beaded wall petal
epidermis (2); the non-glandular, multicellular branched hairs (3)
from the stem leaves or flowers; the broken pieces and branches of
the compound hairs (4) scattered throughout the field; the glandular
hairs (5) with a two-celled stalk; the eight-celled glandular hair
(7) seen in surface view and a side view (8) of a similar hair; the
long, pointed, unicellular non-glandular hair from the tube of the
corolla, the wall irregularly thickened near the apex; the fibres
(9) from the stem; the pollen grains (10) with prominent centrifugal
projections; the conducting cells.
The diagnostic elements of marrubium peregrinum are the multicellular
branched hairs (3) which occur on all parts of the plant, usually
much broken in the powder, with walls many times thicker than the
walls of the hairs found in U. S. P. horehound; the pollen grains
(10) with centrifugal projections and the stalked glandular hairs (5).
INSECT FLOWER STEMS
Insect flower stems are the chief adulterant of insect flowers.
Until the passage of the insecticide law, it was a common practice
to sell (for insect powder) a mixture of powdered stems and flowers.
Since the passage of the law, the presence of the stems in a powder
is supposed to be declared on the label. In spite of the penalties
attached, their presence in a powder is frequently not declared,
as evidenced by a microscopical examination of the insect powders
obtained in the open market.
The structure of powdered insect flower stems (Chart 99) is as
follows:
The epidermal cells of the stems are prominently marked with stoma
and angled, striated wall cells (Fig. 1). On cross-section (Fig.
2) the stem is seen to be made up of epidermal cells with thick
outer and thin side walls (Fig. 2). The T-shaped hairs (Fig. 3) are
longer than those found on any other part of the plant. The fibres
(Fig. 4) are the most characteristic part of the powder. They are
elongated, and the walls are white and slightly porous and of nearly
uniform thickness. They occur free in the field or in groups of two
or more. The cross-section view of these fibres is shown in Fig. 5.
The pith parenchyma (Fig. 6) is abundant and is composed of thick,
porous-walled cells. On cross-section the cells are rounded and are
separated by intercellular spaces. The conducting cells (Fig. 8) vary
from spiral to reticulate.
CHAPTER III
WOODY STEMS
BUCHU STEM
The cross-section of a buchu stem (Plate C), 1.6 millimeters
in diameter, shows a few of the epidermal cells modified into
thick-walled, roughish, unicellular trichomes (1). The remaining
epidermal cells have a thick, wavy outer wall (2). Beneath the
epidermis are several rows of cortical parenchyma cells (3) which
extend to the bast bundles and in which are found the secretory
cavities with the thin-walled secretory cells (4). The bast fibres
(5) occur in continuous bands, varying greatly in size; the walls
are whitish and of variable thickness. Inside the bast fibres, the
small irregular sieve cells (6) occur in groups, surrounded by the
phloem parenchyma (8). The radially elongated cells of the medullary
rays (7) extend outward from the xylem, increasing in number in
the outer portions of the wood, and extending nearly to the bast
fibres. No distinct cambium layer is visible. The conducting cells
(9) occur throughout the xylem surrounded by the wood fibres and
wood parenchyma (10). The latter is not very abundant in buchu. The
medullary rays border on the conducting cells and extend outward to
the phloem. The pith parenchyma cells are nearly circular in outline
and often show a perforated end wall when a cell happens to be cut
just above or below that point.
MATURE BUCHU STEM
In Plate 101-A is shown the cork formation or secondary growth as
seen in the older, larger buchu stems. The wavy epidermis (1),
which is the primary epidermis and which has disappeared on many
portions of the stem, has thin side walls and dark cell contents
(2). Next to the epidermal cells occur several rows of peculiarly
arched cork cells with thick, white outer walls (3) and reddish-brown
cell contents (4). The cork cambium (5) is typical in form, and it
has formed one or two layers of phelloderm cells (6) which have
the same form as the cambium cells but with thicker walls. Next to
the phelloderm occur the cortical parenchyma cells. The remaining
structure of the mature stem is identical with that of Fig. 2.
[Illustration: PLATE 100
CROSS-SECTION OF BUCHU STEMS (_Barosma betulina_ [Berg.],
Barth, and Wendl.)
1. Hairs. 2. Wavy epidermis. 3. Cortical parenchyma. 4. Secretion
cells and cavity. 5. Group of bast fibres. 6. Sieve cells. 7.
Medullary rays. 8. Phloem parenchyma. 9. Vessels. 10. Wood fibres,
and wood parenchyma. 11. Pith parenchyma.]
[Illustration: PLATE 101
_A._ Cross-section of buchu stem (_Barosma betulina_ [Berg.],
Barth. and Wendl.). 1, Outer wall of epidermis; 2, Cell cavity of
epidermal cell; 3, Wall of cork cell; 4, Cavity of cork cell; 5,
Phellogen layer; 6, Divided phellogen cell changing into a cortical
parenchyma cell; 7, Cortical parenchyma cell.
_B._ Cross-section of leptandra rhizome (_Leptandra virginica_
[L.], Nutt.). 1, Parenchyma cells undergoing change in the
composition of their walls; 2, A break in the epidermal tissue; 3,
Parenchyma cells undergoing division.]
POWDERED BUCHU STEM
Powdered buchu stem (Plate 102) has many striking features which
make it easy of identification when mixed with buchu leaves. A
few unicellular, rough, thick, white-walled trichomes (1) occur
distributed throughout the field. They are straight or slightly
curved and vary in length from 40 to 100 microns; in thickness at the
bast they measure from 10 to 22 microns. The central cavity varies
greatly, and in some trichomes seems to have disappeared entirely.
The epidermal cells (2) are very characteristic, occurring singly
or in groups of two or more. The cells from the older stems often
appear reddish brown by transmitted light, while the epidermal cells
from the younger stems appear whitish opaque (porcelain-like).
They are usually six-sided and angular in outline. The cortical
parenchyma cells (3) on transverse view have a rounded cell cavity
and intercellular spaces between the walls. The double walls vary
in thickness, the greatest thickness being about 9 microns. The
parenchyma cells (3) on longitudinal view show square ends and often
contain sphæro-crystalline masses of hesperidin. The thin-walled
sieve cells and the surrounding cells are scarcely ever seen in the
powder. The white-walled pointed stereomes (4) are a characteristic
feature of the powder; they vary greatly in length, in diameter and
in the thickness of their walls. In a number eighty powder the fibres
are mostly broken. The greatest length of the unbroken fibres is
1.25 microns. The thickest wall measured 5 microns and the greatest
observed width was 25 microns. The spiral reticulate and scalariform
thickened conducting cells occur scattered throughout the powder. The
reticulate and scalariform cells usually occur with wood fibres. It
is an interesting fact that the spiral thickening in conducting cells
is usually separate from the side wall and nearly always appears as
indicated at 5. An occasional rosette crystal of calcium oxalate (6)
is seen in the field. The wood parenchyma (7), which makes up a very
small percentage of the xylem, is not readily found in the powder.
The pith parenchyma cells (8) have thick, porous side walls and
perforated side walls. The wood fibres (9) usually occur in masses
surrounding the conducting cells; when occurring singly, the oblique
pores readily distinguish them from the bast fibres.
[Illustration: PLATE 102
POWDERED BUCHU STEMS (_Barosma betulina_ [Berg.],
Barth. and Wendl.).
1. Hairs. 2. Epidermal cells, the larger pieces reddish-brown; the
smaller aggregations white. 3. Transverse cortical parenchyma.
3’ Longitudinal cortical parenchyma with sphæro crystalline
masses of hesperidin. 4. Bast fibres. 5. Spiral, sclariform, and
reticulate vessels. 6. Rosette crystals of calcium oxalate. 7. Wood
parenchyma. 8. Pith parenchyma with porous side and end walls. 9.
Wood fibres.]
The diagnostic elements of powdered buchu stems are:
First, trichomes; secondly, reddish-brown and white-angled epidermal
cells; thirdly, the long, white bast fibres.
CHAPTER IV
BARKS
Barks are all obtained from dicotyledonous plants. In studying
barks there should be ascertained the thickness, arrangement, form,
structure, color, and cell contents of the cells occurring in the
_outer_, _middle_, and _inner_ barks.
The outer bark includes the cork cells and the phellogen layer. The
middle bark includes all the cells occurring between the phellogen
layer and the beginning of the medullary rays. The inner bark
includes the medullary ray cells and all cells associated with them.
The plan of structure of all barks is similar, but in each species of
plant the structure of the bark is uniform and characteristic for the
species.
A great number of drugs consist of the bark of woody plants; for this
reason the bark is considered in a separate chapter from the stem.
WHITE PINE BARK
The cross-section of white pine bark (Plate 103) has the following
structure:
=Outer Bark.= The periderm consists of several layers of
reddish-brown cork cells (1) which are narrow, elongated, and with
thin walls.
=Middle Bark.= The cells forming the middle bark are parenchyma and
secretion cells.
The =parenchyma cells= vary greatly in size, form, and thickness of
the walls. The cells beneath the cork cells and around the secretion
cells are tangentially elongated and oval in shape, while the other
parenchyma cells are more irregular in shape.
The secretion cells are arranged around the schizogenous secretion
cavities. The cells are tangentially elongated, and the walls, which
are slightly papillate, are white.
=Inner Bark.= The cells forming the inner bark are medullary rays,
parenchyma, sieve cells, and storage cavities.
[Illustration: PLATE 103
CROSS-SECTION OF UNROSSED WHITE PINE BARK (_Pinus strobus_, L.)
1. Cork cells of the epidermis. 2. Parenchyma cells filled with
chlorophyl. 3. Intercellular space. 4. Secretion cavity with resin.
5. Secretion cells. 6, One or more circles of parenchyma filled
with chlorophyl. 7. Parenchyma. 8. Medullary rays. 9. Sieve cells.
10. Storage cavities.]
The =medullary rays= form wavy lines. The medullary ray cells are
radially elongated, rectangular in shape, and they contain granular
cell contents. The sieve cells are either square or rectangular in
shape. The walls are thin and white. The storage cavities are either
filled with starch or with prisms and tannin.
POWDERED WHITE PINE BARK
White pine bark (Plate 104) when powdered shows the following
characteristic elements:
The microscopic structure of a powdered white pine is as follows: The
epidermis (1) consists of reddish-brown masses, irregular in outline.
The outer parenchyma cells are of a bright-green color, owing to the
presence of chlorophyll. (The above elements are not usually found in
the rossed bark.) The parenchyma (3) with starch usually occurs in
longitudinal sections accompanied with sieve cells. Often the tissue
separates transversely, showing the medullary rays (4) with their
granular cell contents (9) and the inner parenchyma cells filled with
starch and the surrounding sieve cells.
The crystals are nearly perfect cubes and occur singly (5) or in
groups (6). On the longitudinal section of the bark the crystals
occur in parenchyma cells surrounded by a reddish cell content and
form parallel rows which are very characteristic. The resin occurs
either as white, angled fragments (7) in a water mount, or as
globular mass (8) or as reddish-brown pieces (10). The starch is very
abundant and is distributed through the field. The diagnostic grain
is lens-shaped, with a cleft hilum, which is nearly straight, or
slightly curved, and runs parallel to the long diameter of the grain.
The addition of ferric chlorid T. S. will show the presence of tannin
by forming a dark coloration. The identification of the starch is
facilitated by the addition of a weak Lugol’s solution, which imparts
a blue coloration to the starch grain.
The form, amount, and distribution of the cells composing the bark
differ greatly in different plants.
In cramp bark the cork and phellogen cells are very large, while in
cascara sagrada the phellogen and the cork cells are very small.
[Illustration: PLATE 104
POWDERED WHITE PINE BARK (_Pinus strobus_, L.)
1. Epidermis. 2. Parenchyma cells. 3. Parenchyma with starch. 4.
Medullary rays. 5. Solitary crystals. 6. Solitary crystals and
tannin. 7, 8 and 10. Resin masses. 9. Starch.]
In canella alba bark the periderm is composed of stone cell cork
or stone cells arranged in superimposed rows, which form the outer
layers of the bark.
In white oak and most barks from woody trees the periderm consists of
lifeless parenchyma, medullary rays, sieve cells, bast fibres, and in
some cases stone cells and of phellogen cells.
In young wild cherry, cascara sagrada, and frangula are several
layers of tangentially elongated collenchyma cells with chlorophyll.
In the older barks of the above and in many other barks no
collenchyma cells occur.
In cramp bark and in tulip tree bark the outer layers of the cortical
parenchyma cells are beaded. In most barks there is no beaded walled
parenchyma. The outer layers of most cortical parenchyma cells are
tangentially elongated while the inner parenchyma cells are mostly
circular in outline.
In white oak, cascara sagrada and prickly ash are groups of stone
cells; in the cinnamon barks are bands of stone cells; in cinchona
bark are isolated stone cells. In cramp bark, mezerum, elm, and white
pine bark no stone cells occur.
In frangula, cascara sagrada, cocillina, cinnamon, cinchona,
sassafras, and wild cherry barks the bast fibres occur in groups.
In frangula, cascara sagrada, and cocillina the bast fibres are
surrounded by crystal cells with crystals.
In sassafras bark mucilage cells occur. In canella alba, white pine,
and sassafras barks secretion cells occur; but in most barks no
secretion cells occur.
In sassafras bark the medullary ray cells are nearly as broad as
long; in cramp bark they are elongated and oval in shape. In cascara
sagrada, as in most barks, the cells are longer than broad and
rectangular in shape.
In cascara sagrada the sieve cells are very large; in granatum bark
the sieve cells are very small.
In cassia cinnamon and in canella alba bark the walls of the sieve
cells have collapsed, with the result that the sieve cells have
become partly obliterated.
In witch-hazel, mountain maple, willow, and black walnut are found
prisms; in cramp bark, black haw, wahoo, pomegranate, and cotton root
bark are found rosette crystals; in the cinnamon barks are found
raphides; in cinchona bark, micro-crystals.
In cocillina, frangula, cascara sagrada, white oak, poplar and
Jamaica dogwood barks are found crystal-bearing fibres (Plates 19 and
20).
When studying barks we must consider the kind, structure, and amount
of the periderm; the nature of the phellogen; the nature and amount
of the cortical parenchyma; the occurrence, distribution, and amount
of stone cells, when present; the occurrence and structure of the
bast fibres; the presence or absence of secretion cells; the width,
distribution, and structure of the medullary rays.
CHAPTER V
WOODS
Quite a number of drugs consist of the =wood= of woody plants; such
drugs are quassia, red saunders, white sandalwood, and guaiac.
When studying woods it is necessary to observe the cross, tangential,
and radial sections. Such sections of quassia are shown in Plates
105, 106, and 107. When studying these sections it should be
remembered that while the types of cells forming quassia wood are
similar to the cells forming other woods, still their structure,
arrangement, and amount will vary in a recognizable way in the
different woods.
CROSS-SECTION QUASSIA
Plate 105 is a cross-section of quassia. It has the following
structure:
=Vessels.= The vessels occur singly or in groups of two to eight
cells. The cells are variable in size and shape. The walls are
yellowish white and porous.
=Medullary Rays.= The medullary rays vary from one to five cells in
width.
The =medullary ray cells= are radially elongated and the walls are
strongly porous.
=Wood Parenchyma.= The wood parenchyma cells have thin,
yellowish-white, angled walls.
=Wood Fibres.= The wood fibres have thick, yellowish-white, angled
walls. These cells are smaller in diameter than the wood parenchyma
cells.
RADIAL SECTION QUASSIA
The radial section of quassia (Plate 107) is as follows:
=Vessels.= The vessels appear as in the tangential section.
=Medullary rays.= The medullary rays vary from ten to twenty cells in
height according to the part of the medullary ray bundle cut across.
[Illustration: PLATE 105
CROSS-SECTION OF QUASSIA WOOD (_Picræna excelsa_ [Sw.], Lindl.)
1. Vessels.
2. Medullary rays.
3. Wood parenchyma.
4. Wood fibres.]
[Illustration: PLATE 106
TANGENTIAL SECTION OF QUASSIA WOOD (_Picræna excelsa_ [Sw.], Lindl.)
1. Vessel. 2. Wood parenchyma. 3. Wood fibre. 4. End wall of
medullary ray cell. 5. Medullary ray bundle.]
[Illustration: PLATE 107
RADIAL SECTION OF QUASSIA WOOD (_Picræna excelsa_ [Sw.], Lindl.)
1. Showing the height and length of the medullary rays and cells.
2. Cells with starch.
3. Wood parenchyma and wood fibres.]
The =medullary ray cells= exhibit their height and length. The walls
of the cells are yellowish white and strongly porous.
=Wood Parenchyma.= The wood parenchyma cells have yellowish, thin
walls and blunt end walls.
=Wood Fibres.= The wood fibres have thick, yellowish-white walls, and
the end of the cells are strongly tapering.
TANGENTIAL SECTION QUASSIA
The tangential section of quassia (Plate 106) shows the following
structure:
=Vessels.= The vessels are very long and broad and the yellow walls
are marked with clearly defined pits.
=Medullary Rays.= The tangential section shows the cross-section of
the medullary ray bundle and the cross-section of the medullary ray
cell.
The =medullary ray bundle= varies in width from one to five cells.
The ends of the bundles are always one cell in width, while the
central part of the bundle is frequently five cells in width.
The =medullary ray cell= varies in size, structure, and shape
according to the part of the cell cut across. The cells cut across
the centre show hollow spaces, but the cells cut just above or below
the end wall show a strongly pitted surface. The cells forming the
end of the bundle are larger than the cells forming the centre of the
bundle.
=Wood Parenchyma.= The wood parenchyma cells are greatly elongated
and the walls are thin and yellowish white. The ends of the cells are
blunt.
=Wood Fibres.= The wood fibres are elongated, the walls are thick and
the cells are strongly tapering.
In quassia, white sandalwood, red sandalwood, and guaiac wood are
characteristic crystals.
In quassia the vessels are finely pitted, yellowish, and distinct; in
white sandalwood the vessels are coarsely and sparingly pitted and
white translucent; in red saunders the vessels are coarsely pitted,
bright red and distinct.
When studying woods we must consider the width of the medullary rays,
the structure and cell contents of the medullary ray cells; the
structure, color, and cell contents of the wood parenchyma; also the
wood fibres.
CHAPTER VI
LEAVES
Leaves collectively constitute the greatest manufacturing plant in
the world. Most of the food, clothing, and medicine used by man
is formed as a result of the work of the leaf. The cell contents,
structure, and arrangement of the different cells of the leaf differ
in a marked degree from the cell contents, structure, and arrangement
of the cells in the other organs of the plant. This accounts for the
presence of the large amount of chlorophyll in the leaf, the presence
of stomata, and the peculiar arrangement of the cells.
It should be ascertained if the stomata are above, even with, or
below the epidermis; the nature of the epidermal cells, and, when
present, the nature of the hypodermal cells; the number of layers of
palisade parenchyma and whether it is present on both surfaces of the
leaf, and the nature of the outgrowths from the epidermal cells.
KLIP BUCHU
The cross-section of klip buchu (Plate 108) has the following
structure:
=Epidermis.= The epidermal cells of klip buchu are modified to form
papillæ, the walls are yellowish white, and the papillate portion of
the cell is nearly solid.
=Hypodermis.= The hypodermal cells are never intact because the
mucilage contained in the cells swells when placed in water and
breaks the thin side walls.
=Upper Palisade Parenchyma.= The palisade parenchyma is two layers in
thickness. The cells of the outer layer are greatly elongated and are
packed with chlorophyll. The inner layer of palisade cells is more
irregular, and the cells are much shorter than the cells of the outer
palisade layer.
[Illustration: PLATE 108
CROSS-SECTION OF KLIP BUCHU JUST OVER THE VEIN
_A._ Papillate upper epidermis.
_B._ Hypodermal cells with broken side walls, due to expansion of
mucilage contents.
_C._ Palisade cells, showing two cells filled with chlorophyll.
_D._ Palisade like mesophyll.
_E._ Endodermis.
_F._ Vascular strand of vein.
_G._ Conducting cells with spirally thickened walls.
_H._ Characteristic leaf mesophyll.
_I._ Short, thick palisade cells on the under side of leaf, just
under the vein.
_J._ Under hypodermal cells.
_K._ Papillate under epidermis.]
=Spongy Parenchyma.= The spongy parenchyma cells are branched;
therefore, large intercellular spaces occur between the cells.
=Under Palisade Parenchyma.= The palisade cells of the under
epidermis are short and broad, and they contain fewer chlorophyll
grains than the upper palisade cells of the upper epidermis. These
cells occur only under the veins.
=Under Hypodermis.= The under hypodermal cells are shorter and
broader than the upper hypodermal cells.
=Under Epidermis.= The under epidermal cells are modified to form
papillæ which are similar to the papillæ of the upper epidermis.
=Fibro-Vascular Bundle.= The cells composing the vascular bundle are
sieve cells, vessels, and fibres.
The =sieve cells= are small and the walls are white and angled.
The =vessels= have thick, white, angled walls.
The =bast fibres= are rounded in outline and the walls are thick and
white.
=Endodermis.= The endodermal cells encircle the fibro-vascular
bundles. The cells are large, thin-walled, and oval in shape.
=Secretion Cells.= Near the edges of the leaf are schizogenous
secretion cavities surrounded by thin-walled secretion cells.
POWDERED KLIP BUCHU
When the leaf is powdered (Plate 109), the cells are quite as
characteristic in appearance. The upper epidermal cells (1) have
thick-beaded, yellowish-white walls and papillate outer walls. No
stomata occur on the upper surface. The under epidermis (2) with
numerous stomata, is surrounded by the characteristic guard cells.
The end walls are beaded as on the upper surface. The palisade cells
(3) appear as in the cross-section. The conducting cells (4 and 4)
are of the spiral and pitted type. The papillæ (5 and 5) are very
abundant in the powder and very characteristic. The fragments of the
epidermis (6) are also abundant. The mesophyll (7) is characteristic,
as it retains its form when powdered. The fibres (8) are usually
associated with the conducting cells; occasionally they are found
free as in the illustration.
[Illustration: PLATE 109
POWDERED KLIP BUCHU
1. Upper epidermis. 2. Under epidermis. 3. Palisade cells with
chlorophyll. 4 and 4. Conducting cells. 5 and 5. Papillæ. 6.
Fragments of the epidermis. 7. Mesophyll. 8. Fibres.]
MOUNTAIN LAUREL
=Epidermis.= The epidermal cells of mountain laurel are occasionally
modified, as unicellular hairs (Plate 110, Fig. 1), particularly in
the region of the veins. The ordinary epidermal cells have thick
outer walls and thin inner walls. Beneath many of the epidermal cells
are large air-spaces.
=Upper Palisade Parenchyma.= The palisade parenchyma vary from four
to five layers. The inner palisade cells are shorter and broader than
the outer layer of cells.
=Parenchyma.= The parenchyma cells (Fig. 4) are rounded in form
and they are arranged in the form of columns which are one cell in
thickness above, but two to three cells in thickness near the under
epidermis. Between each chain of cells is a larger intercellular
space (Fig. 6). In a few of the cells are large rosette crystals.
=Under Epidermis.= The under epidermal cells are uniformly smaller
than the upper epidermal cells.
It is thus seen that mountain laurel leaf has no hypodermal cells;
no spongy parenchyma; no under palisade cells; no under hypodermal
cells, and no secretion cavities.
TRAILING ARBUTUS
=Epidermis.= The epidermal cells of the trailing arbutus (Plate 111,
Fig. 2) are variable in size. Many of the cells are modified, as
guard cells (Fig. 1).
=Parenchyma.= The parenchyma cells are round and they are compactly
arranged (Fig. 3) on the upper side of the leaf, but on the under
side they are arranged in round, small, intercellular spaces (Fig.
5). In some of the intercellular spaces are rosette crystals (Fig. 7).
=Under Epidermis.= The under epidermal cells are smaller than the
upper epidermal cells.
It will be seen that the structure of trailing arbutus leaf is very
simple and that its structure is different from that of klip buchu
and mountain laurel.
The structure of powdered leaves is very variable, yet characteristic
for a given species. The leaves from the insect flower plant are
collected with the stems, and ground and sold as a substitute for
insect flowers. These leaves, when powdered, show the following
structure (Plate 112):
[Illustration: PLATE 110
CROSS-SECTION MOUNTAIN LAUREL (_Kalmia latifolia_, L.)
1. Hair. 2. Epidermis. 3. Palisade parenchyma. 4. Parenchyma. 5.
Under epidermis. 6. Intercellular space. 7. Rosette crystal. 8.
Chlorophyll.]
[Illustration: PLATE 111
CROSS-SECTION TRAILING ARBUTUS LEAF (_Epigæa repens_, L.)
1. Stomata. 2. Epidermis. 3. Parenchyma. 4. Cell with chlorophyll.
5. Intercellular space. 6. Under epidermis. 7. Rosette crystal.]
Both the upper and lower epidermis have stomata (Figs. 1 and 2), but
they differ in that the surrounding cells of the upper epidermis
are wavy, while the corresponding cells of the under epidermis are
similar, though the under epidermis has many attached hairs (Figs.
3 and 4). The T-shaped hairs form the most abundant element of the
powder. They are similar in structure to those found on the scales
and stem. Fragments of the mesophyll have round cells and contain
chlorophyll (Fig. 6). The conducting cells are spiral or reticulate.
The different cells of the leaf differ greatly in structure, in
amount, and in arrangement. In uva-ursi, boldus, pilocarpus,
eucalyptus, and chimaphila leaves the outer walls of the epidermal
cell is very thick. In uva-ursi leaves this thick wall appears bluish
green when viewed under low power of the microscope.
In belladonna, stramonium, henbane, peppermint, spearmint, digitalis,
and horehound, the outer wall of the epidermal cells is thin.
In witch-hazel, stramonium, coca, phytolacca, and peppermint there is
a single layer of palisade parenchyma on the upper surface only of
the leaf.
In senna there is one layer of palisade parenchyma on the upper and
one layer on the under side of the leaf. In matico and tea leaves
there are two layers of spongy parenchyma on the upper side of the
leaf.
In chestnut leaves there are three layers of palisade parenchyma on
the upper side of the leaf.
In eucalyptus leaves the entire central part of the leaf, with the
exception of the secretion cells and fibro-vascular bundle, is made
up of the palisade parenchyma.
In some leaves no palisade parenchyma occurs. Trailing arbutus (Plate
111) is an example of such a leaf.
In stramonium leaves the spongy parenchyma is strongly branched; in
mountain laurel the spongy parenchyma is mostly non-branched and
circular in form, as in trailing arbutus (Plate 111, Fig. 3), and as
occurs in the midrib portion of most leaves.
[Illustration: PLATE 112
POWDERED INSECT FLOWER LEAVES
(_Chrysanthemum cinerariifolium_ [Trev.], Vis.)
1. Upper epidermis. 2. Under epidermis showing stoma and hair
scar. 3. Cross-section of under epidermis with attached hair. 4.
Cross-section of upper epidermis. 5. Hairs. 6. Mesophyll with
chlorophyll bodies. 7. Conducting cells.]
In stramonium and chestnut are found rosette crystals. In henbane,
coca, and senna are found prisms. In belladonna, scapola, and
tobacco leaves are found micro-crystals. In most leaves no crystals
occur. In witch-hazel and tea leaves stone cells occur, but in most
leaves there are no stone cells. In eucalyptus, thyme, jaborandi,
buchu, rosemary, and white pine leaves are secretion cells; while
in belladonna, stramonium cells occur. In senna and coca leaves are
crystal-bearing fibres; most leaves do not have crystal-bearing
fibres.
In chimaphila and uva-ursi there are no outgrowths from the epidermal
cells.
In senna, witch-hazel, chestnut, and coca, numerous non-glandular
hairs occur on the epidermis. In tobacco, belladonna, henbane,
pennyroyal, peppermint, and spearmint both glandular and
non-glandular hairs occur on the epidermis.
When studying leaves there should be considered the absence or
presence of outgrowths and their nature; the nature of the epidermis
and, when present, the number of layers of the hypodermis; the nature
of the stoma, whether raised above, even with, or below the level
of the epidermis; the number of layers, and the distribution, when
present, of the palisade parenchyma; the form and amount of the
spongy parenchyma; the absence or presence of secretion cells; the
nature and form of the fibro-vascular bundles, and the nature and
amount of the organic and inorganic cell contents.
CHAPTER VII
FLOWERS
The histological structure of flowers is readily seen in the powder;
therefore, in studying flowers, it is not necessary to section
the various parts. Each part of the flower should be isolated and
powdered separately and each separated part studied. In each case
the powders will contain surface, cross-, and radial sections of the
parts powdered. While studying flowers, special attention should be
given to the pollen grains, to the papillæ of the petals, to the
papillæ of the stigma, and, in certain flowers, to the style tissue.
In the composite flowers special attention should also be given to
the involucre scales, to the scales of receptacle, and, when present,
to the pappus. In addition, attention must be given to secretion
cavities, as in cloves.
POLLEN GRAINS
Pollen grains are one of the most characteristic elements found in
powdered flowers, because they are so small that they are not broken
up when the drug is milled.
The two principal groups of pollen grains are, first, those with
non-spiny walls (Plate 113); and, secondly, those with spiny walls
(Plate 114), as shown in the two charts.
In lavender flowers the pollen grains have six constrictions of the
outer wall. This wall is slightly striated and the cell contents are
granular.
In clover flowers the pollen grains are mostly rounded in outline,
the wall is uniformly thickened, and cell contents are coarsely
granular.
In belladonna flowers the pollen grains terminate in three blunt
points.
In Spanish saffron the pollen grains are spherical and the cell
contents are granular.
[Illustration: PLATE 113
SMOOTH-WALLED POLLEN GRAINS
1. Cloves (_Eugenia caryophyllata_, Thunb.). 2. Santonica
(_Artemisia pauciflora_, Weber). 3. Elder (_Sambucus canadensis_,
L.). 4. Century minor (_Erythræa centaurium_ [L.], Pers.). 5. Pichi
(_Fabiana imbricata_, R. and P.). 6. Cyani. 7. Lavender (_Lavandula
officinalis_, Chaix.). 8. Clover (_Trifolium pratense_, L.). 9.
Belladonna (_Atropa belladonna_, L.). 10. Spanish saffron (_Crocus
sativus_, L.).]
[Illustration: PLATE 114
SPINY WALLED POLLEN GRAINS
1. Anthemis (_Anthemis nobilis_, L.).
2. Arnica (_Arnica montana_, L.).
3. Calendula (_Calendula officinalis_, L.).
4. Cassia flowers.
5. American saffron (_Carthamus tinctorius_, L.).
6. Blue malva flowers (_Malva sylvestris_, L.).]
The non-spiny-walled pollen grains differ not only in microscopic
appearance, but also in size. Clove pollen grains are the smallest,
while Spanish saffron pollen grains are the largest.
NON-SPINY-WALLED POLLEN GRAINS
In cloves the pollen grains show a six-sided, angled cavity and an
outer wall which terminates in three slightly pointed, narrowly
notched portions, separated by nearly straight walls.
In santonica the pollen grains have smooth, unequally thickened
walls, which are strongly constricted at three points, the outline
resembling three half-circles placed together.
In elder flowers the pollen grains appear circular or three-parted.
The wall is of nearly uniform thickness, even at the constricted part
of the grain.
In century minor the pollen grains show three pronounced
restrictions. The wall at these points is very thin. In pichi
flowers the pollen grains are either circular or three-sided and
three-pointed. Inside of each point there is a nearly white pore. In
some of the grains the pollen tube has grown out of one of the pores.
In cyani flowers the pollen grains are longer than broad and the cell
contents appear to be divided into two end portions and an elevated
middle portion.
SPINY-WALLED POLLEN GRAINS
In anthemis the pollen grains have unequally thickened walls
constricted in three places. The spines are short, broad at the base,
and sharp-pointed.
In arnica flowers the pollen grains show three light-colored pores
and numerous short spines.
In calendula flowers the pollen grains show one or more pores,
typically three pores. These pores appear as white spots, and the
wall immediately over the pore is smooth and thinner than the
remaining part of the wall; the spines are very numerous.
In cassia flower pollen grains the outer wall is extended into a
number of rounded projections which are frequently arranged in sets
of fours.
In American saffron flowers the pollen grains show one, two, or three
light-colored pores; the spines are short and broad.
In blue malva flowers the pollen grains are spherical and the outer
wall extends into numerous spinelike projections.
It will be observed that the spiny-walled pollen grains differ
greatly in size, the smallest being the pollen grain of anthemis and
the largest being the pollen grain of blue malva flowers.
In matricaria are numerous, greenish-brown, spiny-walled pollen
grains. In anthemis are multicellular, uniseriate non-glandular hairs
with three or four short, broad, yellow-walled basal cells and a
greatly elongated, thin, gray-walled apical cell.
In arnica are multiseriated branched hairs of the pappus, and
numerous large, yellowish, spiny-walled pollen grains.
STIGMA PAPILLÆ
The =papillæ of the stigma= of most flowers form a characteristic
element even when the flower is powdered. In the case of composite
flowers the papillæ of the disk and ray flowers differ. In American
saffron the papillæ of the style differ in a recognizable way from
the papillæ of the stigma.
The papillæ of the stigma of the ray and disk flowers of arnica,
anthemis, matricaria, and insect flowers differ greatly. Even the
papillæ of the stigma of the ray and disk flowers differ. In all
cases observed the papillæ of the ray flowers are smaller than the
papillæ of the disk flowers.
The papillæ of the stigma of saffron (Plate 115, Fig. 3) are long and
tubular. These papillæ are nearly uniform in diameter, and the apex
is blunt and rounded. The wall is slightly granular in appearance.
The papillæ of the stigma of American saffron (Plate 116, Fig. 2) are
short and tubular. Each papilla is broadest at the base and tapers to
a slender point. The papillæ of that part of the style which emerges
from the corolla (Plate 116, Fig. 1) are large and curved, and the
walls are very thick. The apex of the papilla is frequently solid.
The papillæ of the stigma of the ray flowers of anthemis (Plate 117,
Fig. 1) have thin, slightly striated walls; while the papillæ of the
stigma of the disk flowers (Plate 117, Fig. 2) are longer, the walls
are thicker, and the cell content is denser.
[Illustration: PLATE 115
PAPILLÆ
1. Arnica ray flowers (_Arnica montana_, L.).
2. Insect flower disk (_Chrysanthemum cinerariifolium_ [Trev.], Vis.).
3. True saffron (_Crocus sativus_, L.).]
[Illustration: PLATE 116
PAPILLÆ OF STIGMAS
1. Stigma papillæ of American saffron (_Carthamus tinctorius_, L.)
from that part of the style that emerges from the corolla.
2. Papillæ from the upper part of the stigma of American saffron.
3. Papillæ of the stigma of the disk flowers of arnica (_Arnica
montana_, L.).]
[Illustration: PLATE 117
PAPILLÆ OF STIGMAS
1. Stigma papillæ of the ligulate flowers of anthemis (_Anthemis
nobilis_, L.).
2. Stigma papillæ of the tubular flowers of anthemis.
3. Stigma papillæ of the ligulate flowers of matricaria
(_Matricaria chamomilla_, L.).
4. Stigma papillæ of the disk flowers of matricaria.
5. Stigma papillæ of the ligulate flowers of insect flower
(_Chrysanthemum cinerariifolium_ [Trev.], Vis.).]
The papillæ of the stigma of the ray (Plate 117, Fig. 3) and disk
flowers (Plate 117, Fig. 5) of matricaria are similar in structure,
but the papillæ of the disk flowers are larger.
The papillæ of the stigma of the ligulate flowers of insect flowers
(Plate 117, Fig. 5) are tubular; the walls are striated, and in each
papilla there is a small yellow globule, while the papillæ of the
disk flowers (Plate 115, Fig. 2) are long and tubular, and the walls
are thick.
The papillæ of the stigma of the ray flowers of arnica (Plate 115,
Fig. 1) are very short and tubular. The walls are thin and the cell
contents appear as small, bright-yellow globules, while the papillæ
of the stigma of the disk flowers (Plate 116, Fig. 3) are broadest at
the base, the apex is pointed, and the yellow globules are larger.
The =solitary= hairs are divided into the branched and non-branched
hairs.
POWDERED INSECT FLOWERS
The microscopic examination of insect powder is difficult for the
reason that there are so many elements to be constantly kept in mind.
The parts of the flower which contribute characteristic cells are the
stem, involucre, ray flowers, disk flowers, and the receptacle. In
each of these parts there are many different types of cells.
There are practically two types of flowers found in insect powder of
commerce: first, closed or immature flowers, and secondly, open or
mature flowers. As explained above, the half-open flowers consist
largely of the two above-named varieties. Let us first consider the
structure of the closed insect flowers as illustrated in Plate 118.
[Illustration: PLATE 118
POWDERED CLOSED INSECT FLOWER
(_Chrysanthemum cinerariifolium_, [Trev.] Vis.)
1. Edge of scale. 2. Fibre of scale. 3. Hairs. 4. Upper epidermis
of ray flower. 5. Under epidermis of ray flower. 6. Cross-section
of ray petal. 7. Parenchyma of ray flowers with crystals. 8. Lobe
of disk petal. 9. Filament tissue. 10. Calyx tissue, 11. Lobe of
stamen. 12. Pollen. 13. Papillæ of stigma. 14. Secretion cavity
with surrounding cells. 15. Parenchyma of the receptacle.]
The involucre has many characteristic cells. The more prominent
ones seen in the powder are the edge of the scale with the attached
hair (Fig. 1). These hairs (Fig. 3) are T-shaped. The terminal cell
is expanded laterally, and it terminates in two points. Connecting
the terminal cell with the epidermis are two or three cells which
are slightly longer than broad. In the powder the terminal cell is
usually attached to fragments only of the supporting cells. Fibres of
the bracts have thick, wavy, porous walls, and they have a tendency
to occur in masses. The upper epidermis (Fig. 4) of the ray-flower
petal is prominently papillate. The under epidermis consists of
wavy cells without papillæ. Another view of the papillæ is shown in
Fig. 6. The parenchyma of the ray flowers (Fig. 7) contain cubical
crystals. The lobe of the disk-flower petal (Fig. 8) is papillate at
the end, the terminal cells have thick outer and thin inner walls.
The filament tissue (Fig. 9) is composed of nearly square cells. The
calyx tissue (Fig. 10) is made up of thin-walled cells with slightly
papillate margins. The lobe of the stamen (Fig. 11) consists of
nearly uniform epidermal cells which are in contact throughout their
long diameter, while the hypodermal cells are thin-walled and angled.
The pollen grains (Fig. 12) are dark yellowish green, thin, and the
wall does not appear perforated by pores. The papillæ of the stigma
(Fig. 13) are clustered, club-shaped, and nearly white in color. They
are usually found detached in the powder. All parts of the pistil
contain secreting cells, but the most conspicuous secreting cavities
(Fig. 14) are those of the ovary. These cavities appear brownish in
color and are surrounded by small cells which appear indistinct on
account of the great number of superimposed cells. The parenchyma of
the receptacle occurs in fragments which have strongly marked porous
walls.
OPEN INSECT FLOWERS
Many of the structures of open insect flowers (Plate 119) are
similar to those found in the closed flower. There is practically
no difference in the edge of the scale (Fig. 1); or the fibre of
the scale (Fig. 2); or the T-shaped hairs (Fig. 3); or the upper
epidermis of the ray flower (Fig. 4); or the under epidermis of the
ray flower (Fig. 5); or the cross-section of the ray petal (Fig.
6); or the lobe of the disk petal (Fig. 7); or the filament tissue
(Fig. 8); or the lobe of the stamen (Fig. 9); or the papillæ of
the stigma (Fig. 12); or the parenchyma of the receptacle (Fig.
15). The difference in structure is found, first, in the involucre
scales, which are more fibrous than the scales of the closed flowers;
secondly, in the pollen (Fig. 11), which is less abundant than in the
closed flower; it is also lighter in color and usually shows the wall
perforated by three pores; thirdly, the outer layers of the achene
consist of thick, porous-walled stone cells (Fig. 13), which occur
singly or in groups; fourthly, the secretion cavity is broader and
darker in color (Fig. 14). These differences enable one at once to
distinguish between the closed and open insect flowers. Now, since
the half-closed flowers consist almost wholly of a mixture of equal
parts of closed and open flowers, it follows that the elements of
these two flowers will be mixed in about equal proportions. Thus
we are able to distinguish microscopically the three commercial
varieties of insect powder--namely, closed insect flowers, open
insect flowers, and half-open insect flowers.
[Illustration: PLATE 119
POWDERED OPEN INSECT FLOWER
(_Chrysanthemum cinerariifolium_, [Trev.] Vis.)
1. Edge of involucre scale. 2. Fibres of involucre scale. 3.
Hairs. 4. Upper epidermis of ray flower. 5. Under epidermis of ray
flower. 6. Cross-section of ray petal. 7. Lobe of disk flower. 8.
Filament tissue. 9. Lobe of stamen. 10. Calyx tissue, 11. Pollen.
12. Papillæ of the stigma. 13. Stone cells from the achene and
cross-section of achene. 14. Secretion cavity with surrounding
cells. 15. Parenchyma of the receptacle.]
Insect flowers are the most valuable vegetable insecticide known; yet
much of its effectiveness is destroyed by the adulterants which are
so readily identified by the compound microscope.
POWDERED WHITE DAISIES
A common adulterant found in open insect flowers is the flower-heads
of European daisy (_C. leucanthemum_). Examination of powdered
flowers exported from Europe shows that the entire flower-head is
ground and mixed with the insect flowers. In the cheaper varieties
of open flowers, only the tubular flowers are added after they have
been separated from the heads by crushing and sifting. These tubular
flowers so closely resemble the tubular flowers of the true insect
flowers that it is practically impossible to distinguish between them
macroscopically. The quickest and surest way to identify them is
to reduce a portion of the flowers to a fine powder and examine it
microscopically.
Certain structures of the white daisies (Plate 120) are somewhat
similar to those found in insect flowers. These structures are the
papillæ of the ray petal (Figs. 3, 5, and 13), the lobe of the disk
petal (Fig. 14), and the lobe of the stamen and the pollen (Fig. 8).
The differences are as follows: The under epidermis of the ray
flowers is composed of wavy cells which are more elongated than the
ray flowers of the under epidermis of the ray petal of insect flower.
The filament tissue is made up of slightly beaded cells instead of
smooth-walled cells. The papillæ of the stigma are smaller than the
papillæ of insect flowers. The most striking difference is found
in the structure of the achene. The epidermal tissue of the achene
is composed of palisade cells (Fig. 10), which in the mature form
have thick white walls and scarcely any cavity. These cells swell
perceptibly when placed in water. The other striking feature of the
achene is the bright red resin masses which occur free in the field.
Even a small trace of daisies in insect powder can be identified.
[Illustration: PLATE 120
POWDERED WHITE DAISIES (_Chrysanthemum leucanthemum_, L.)
1 and 2. Scale tissue. 3, 5 and 13. Papillæ of petals. 4. Scale
tissue. 6. Lobe of ray petal. 7. Filament tissue. 8. Pollen. 9.
Papillæ of stigma. 10. Palisade cells of achene. 11. Resin masses.
12. Parenchyma of receptacle. 14. Lobe of dish petal.]
When studying flowers there should be considered the number and
structure of pollen grains; the nature of the papillæ of the stigma
and the petals; the nature of the hairs of the corolla and calyx,
when present. In the composite flowers we should also consider the
structure of the involucre scales, and, when present, the structure
of the receptacle scales, as in the case of anthemus, and of the
pappus hairs, as in the flowers of arnica, boneset, grindelia, and
aromatic goldenrod.
CHAPTER VIII
FRUITS
There is great variation in the structure of fruits, such a
variation, in fact, that no one fruit has a structure typical of all
the other fruits. Each fruit, however, has a pericarp and one or more
seeds. The amount and structure of the cells forming the pericarp
and the seeds of fruits differ in different fruits, but for each
fruit there is a normal amount of, and a characteristic, cellular
structure. Nearly all the important medicinal fruits are cremocarps
or umbelliferous fruits.
The plan of structure of cremocarps is similar, but they all have a
different cellular structure. The epidermis may be simple or modified
as papillæ or hairs. The secretion cavities may be absent (conium),
or, when present, variable in number--cultivated celery seed has six,
wild celery seed up to twelve, and anise up to twenty. The vascular
bundles may be large or small. The endocarp cells may be two or more
layers in thickness. The spermoderm may be thin or thick.
The endosperm cells may vary in size and the cell contents may vary.
CELERY FRUIT
The fruit of celery (Plate 121), like other umbelliferous fruits, is
composed of the pericarp and the seed.
The pericarp is composed of epicarp cells, mesocarp cells, endocarp
cells, and in each rib a vascular bundle. The seed is composed of
the spermoderm, endosperm, and embryo. Each of these parts has a
characteristic structure.
=Epicarp=. The cells of the epicarp (Fig. 1) are papillæ and the
outer wall is striated. The papillæ do not show, however, unless
the cell is cut across the centre, which is the point at which the
papillæ are located.
[Illustration: PLATE 121
CROSS-SECTION OF CELERY FRUIT (_Apium graveolens_, L.)
1. Epicarp. 2. Mesocarp. 3. Vascular bundle. 4. Endocarp. 5.
Spermoderm. 6. Endosperm. 7. Secretion cavity.]
[Illustration: PLATE 122
DIAGRAMMATIC DRAWING OF THE
1. Cross-section of wild celery seed (_Apium graveolens_, L.).
2. Cross-section of cultivated celery seed (_Apium graveolens_, L.).]
=Mesocarp=. In the rib part of the mesocarp (Fig. 2) is a vascular
bundle, and between the ribs one or more secretion cavities. The
vascular bundles are small and are surrounded by irregular-shaped
mesocarp cells.
The =secretion cavities= (Fig. 7) are oval in form and the tissue
bordering the cavity is reddish brown in color. The mesocarp cells
around the secretion cavities are more elongated than the other
mesocarp cells.
=Endocarp=. The endocarp cells are three layers in thickness. These
cells are elongated transversely (Fig. 4).
=Spermoderm=. The cells of the spermoderm are indistinct, compressed,
and dark brown in color (Fig. 5).
=Endosperm=. The endosperm cells (Fig. 6) make up the greater part
of the fruit. The walls which are common to two cells are thick,
non-beaded, and non-pitted, and the cavities of the cells are filled
with aleurone grains.
=Embryo=. The embryo cells, which show only in certain sections, are
similar to endosperm cells.
In anise, hops, sumac, and cumin fruits are characteristic hairs.
In star anise, sabal, allspice, cubeb, pepper, juniper, buckthorn,
and phytolacca fruits are stone cells.
In cubeb, pepper, and cardamon are characteristic masses of aggregate
starch.
In sabal, allspice, and juniper are characteristic secretion cells.
In all the umbelliferous fruits, with the exception of conium, are
yellow to brown secretion cavities.
In cubeb and pepper is aggregate starch. Colocynth contains many
single and double spiral vessels.
Bitter orange contains solitary crystals and spongy parenchyma.
When studying fruits we must consider the nature of the epicarp
cells--whether simple or modified as papillæ or hairs; the form and
structure of the mesocarp cells; the number, size, and structure of
the vascular bundle; the size and number of the secretion cells or
cavities; the number of layers and the structure of the endocarp
cells; the number of layers of stone cells--when present; the color
and width of the spermoderm layer; the structure and cell contents of
the endosperm cells; the nature of the embryo cells, and the nature
of the cell contents.
CHAPTER IX
SEEDS
Seeds are very variable in structure, so much so, in fact, that
scarcely any two seeds have a similar structure. It is necessary,
therefore, when examining seeds, to compare the structure of the seed
under examination with authentic plates or with the section of a
genuine seed. The layers of the seed are the spermoderm, perisperm,
endosperm, and embryo. In some seeds the spermoderm forms the greater
part of the seed; in others the perisperm is greatest in amount;
in still others the cotyledons make up most of the seed, as in the
mustards. The cells forming these different layers differ in form,
structure, and number; therefore it is not difficult to distinguish
and to differentiate between the different seeds when viewed as a
section or as a powder. Almond is studied because it has most of the
layers and cells found in seeds.
SPERMODERM
The =spermoderm= is the thin, brown, granular-appearing skin of the
almond. The layers of the spermoderm are the epidermis, the hypoderm,
the middle layers, and the inner epidermis.
The =epidermis= consists of radially elongated, thick-walled stone
cells which occur alone or in groups of two or more, but seldom as
a continuous layer. The upper or outer part of the stone cells is
non-porous, but the inner walls are strongly porous (Plate 123, Fig.
1).
The =hypoderm=. The cells forming the hypoderm are compressed, the
wall structure is practically indistinguishable, and the whole mass
is reddish brown (Plate 123, Fig. 2).
Occurring in this brown layer are several vascular bundles (Plate
123, Fig. 3).
[Illustration: PLATE 123
CROSS-SECTION SWEET ALMOND SEED
1. Epidermis. 2. Hypoderm. 3. Vascular bundle. 4. Middle layer. 5.
Inner epidermis. 6. Endosperm. 7. Outer layer of the embryo. 8.
Inner layers of the embryo.]
The =middle layers=. The cells forming the middle layers (Fig. 4)
have thin, wavy, light-colored walls which are frequently compressed,
and it is with much difficulty that their outlines are made out.
The =inner epidermis=. The cells forming the inner epidermis are
rectangular in form, and they contain reddish-brown cell contents
(Plate 123, Fig. 5).
ENDOSPERM
The =endosperm=. The cells forming the endosperm are large,
rectangular in outline, usually one layer thick, and they contain
aleurone grains.
EMBRYO
The =embryo=. The cells forming the outer layer of the embryo are
smaller than the inner layers, and they are immediately inward from
the layer of endosperm cells (Plate 123, Fig. 7).
The cells forming the greater part of the embryo are large, rounded,
and they contain aleurone grains and fixed oil (Plate 123, Fig. 8).
In white and black mustard are characteristic mucilage and palisade
cells.
In mix vomica, stropanthus, and St. Ignatius’s bean are
characteristic hairs.
In physostigma and kola are characteristic starch grains.
In henbane, capsicum, stramonium, lobelia, and belladonna seeds are
characteristic epidermal cells.
In areca nut, colchicum, saw palmetto, and nux vomica are
characteristic thick-walled, reserve cellulose cells.
In cardamon seed are aggregate starch masses with irregular outlines.
In bitter and sweet almond, linseed, pepo, and stropanthus are
aleurone grains.
In bitter and sweet almonds are stone cells.
In linseed, quince seed, and in white and black mustard are epidermal
cells with mucilaginous walls and contents, etc.
CHAPTER X
ARRANGEMENT OF VASCULAR BUNDLES
Having familiarized ourselves with the different types of mechanical
and conducting cells, we shall now consider the different ways
in which these cells are associated to form the =vascular= and
=fibro-vascular bundles=.
The simplest form of the vascular bundle occurs in petals, floral
bracts, and leaves. In these parts the vascular bundle is made up of
conducting cells only.
In the great majority of cases, however, the conducting cells are
associated with mechanical cells to form the fibro-vascular bundle.
The fibro-vascular bundle is made up of, first, the =phloem=,
which consists of sieve tubes, companion cells, bast fibres, and
parenchyma; secondly, of the =xylem=, composed of vessels and
tracheids, wood fibres and wood parenchyma; thirdly, of medullary
rays (restricted to certain types); and fourthly, of the bundle
sheath (restricted to certain types).
TYPES OF FIBRO-VASCULAR BUNDLES
There are three well-defined types of the fibro-vascular bundle,
namely, the =radial=, the =concentric=, and the =collateral= types.
RADIAL VASCULAR BUNDLES
The radial type of bundle is met with most frequently in
monocotyledonous roots.
In this form (Plate 114) the xylem forms radial bands of tissue
which alternate with isolated groups of phloem. The space between
the phloem and xylem is filled in with either parenchyma or fibres,
or both. In some cases the vessels of the xylem meet in the centre
of the root, while in other cases the centre of the stem is occupied
by pith parenchyma. Each bundle is surrounded by parenchyma cells,
and in iris, calamus, and veratrum, rhizomes, and endodermis,
surrounds the bundles located in the centre of the stem, consisting
of thin-walled (mechanical) cells.
[Illustration: PLATE 124
CROSS-SECTION OF A RADIAL VASCULAR BUNDLE OF SKUNK CABBAGE ROOT
(_Symplocarpus fœtidus_ [L.], Nutt.)
1. Vessels.
2. Bundle sheath.
3. Parenchyma.
4. Sieve cells.]
[Illustration: PLATE 125
CROSS-SECTION OF A PHLOEM-CENTRIC BUNDLE OF CALAMUS RHIZOME
(_Acorus calamus_, L.)
1. Vessels.
2. Sieve cells.
3. Phloem parenchyma.
4. Parenchyma surrounding the bundles.]
In sarsaparilla root, the pith is composed of thick-walled, porous
pith parenchyma cells with starch. Outside the pith are arranged
radial bands of oval vessels which decrease in size toward the
periphery. Between the ends of these bands occur isolated groups of
sieve cells.
Surrounding the sieve cells and vessels are thick-walled, angled
fibres.
External to these cells is an endodermis composed of lignified
brownish-colored cells one layer in thickness.
CONCENTRIC VASCULAR BUNDLES
There are two principal types of the concentric bundle, namely,
xylem-centric, in which the xylem is centric and the phloem is
peripheral, as in veratrum root; and phloem-centric (Plate 125), in
which the phloem is centric and the xylem peripheral, as in calamus
rhizome.
COLLATERAL VASCULAR BUNDLES
There are three types of collateral vascular bundles--namely, closed
collateral, bi-collateral, and open collateral.
In the closed collateral bundle the phloem and xylem are not
separated by a cambium layer, and in many cases the bundle is
surrounded by thick, angled walled fibres, as in palm stem. The term
closed bundle refers to the fact that there is no cambium between the
xylem and phloem, therefore the bundle is “closed” to further growth,
and not to the fact that it is frequently surrounded by fibres which
prevent further growth. In podophyllum stem (Plate 126) the xylem
portion of the bundle faces the centre of the stem and the phloem
portion of the bundle faces the epidermis. The xylem and phloem are
separated by a cambium layer, and both are surrounded by thick-walled
angled fibres which are the chief mechanical cells of the stem. This
bundle is, in fact, mechanically closed, but not physiologically
because a cambium is present.
[Illustration: PLATE 126
CROSS-SECTION OF A CLOSED COLLATERAL BUNDLE OF MANDRAKE STEM
(_Podophyllum peltatum_, L.)
1. Vessels.
2. Sieve cells.
3. Cambium.
4. Fibres.
5. Parenchyma.
6. Intercellular space.]
[Illustration: PLATE 127
BI-COLLATERAL BUNDLE OF PUMPKIN STEM (_Curcurbita pepo_, L.)
1. Vessels.
2. Sieve tubes.]
BI-COLLATERAL VASCULAR BUNDLES
In the bi-collateral vascular bundle (Plate 127) the xylem is in
between two groups of phloem--namely, an inner group and an outer
group.
In pumpkin stem a bundle occurs in each angle of the stem. The entire
bundle is surrounded by parenchyma cells.
In an individual bundle the xylem consists of large circular vessels
and a phloem containing large sieve cells, many of which show the
yellow porous sieve plates.
OPEN COLLATERAL VASCULAR BUNDLES
In the open collateral bundle (Plate 100) the xylem and phloem are
separated by the cambium layer, which, through its divisions, causes
the stem to increase in thickness each year. This type of bundle is
characteristic of the stems and roots of dicotyledonous plants.
The bi-collateral bundle occurs in many leaves. The xylem in such
cases is central, the phloem strands occupying upper and lower
peripheral positions.
INDEX
Abbé condenser, illustration, 11
Absorption tissue, introduction, 121
tissue of leaves, 125
Aerating tissue, introduction, 151
Annular vessels, illustration of, 129
Bark, of white pine powdered, description of, 250
of white pine powdered, illustration of, 251
unrossed white pine, cross-section, illustration of, 249
Barks, description of, 248
diagnostic structures of, 253
structural variations of, 252
Base sledge microtome, 35
sledge microtome, illustration, 35
Bast fibres, 89
branched, 92
branched, illustrations, 95
crystal bearing, 90, 92
description of, 100
groups of, illustrations, 102
non-porous and non-striated, 96
non-porous and non-striated, illustrations, 101
non-porous and striated, 96
occurrence in powdered drugs, 103
of barks, illustrations, 91, 93, 94
of klip buchu leaf, 262
of ruellia rhizome, 226
of ruellia root, 223
of ruellia stem, 235
of spigelia stem, 235
porous and non-striated, illustrations, 98
porous and striated, 92
porous and striated, illustrations, 97
storage function of, 179
striated and non-porous, illustrations of, 99
Bi-collateral vascular bundles, description of, 298
Buchu stems, cross-section, illustration of, 243
cross-section, illustration of, 244
powdered, description of, 245
powdered, illustration of, 246
Cambium of pink root, 221
of ruellia rhizome, 226
of ruellia stem, 237
of spigelia rhizome, 223
of spigelia stem, 235
Camera lucida, 22
illustrations, 22
Care of microscope, 28
Celery fruit, diagrammatic drawing of, 287
Cell contents, 182
aleurone grains, 197
aleurone grains, description of, 198
aleurone grains, form of, 197
aleurone grains, structure of, 197
aleurone grains, tests for, 198
chlorophyll, 182
crystals, 200
crystals, composition of, 200
crystals, micro-, 200
crystals, raphides, 200
crystals, rosette, 200
crystals, solitary, variation of, 205
cystoliths, 210
cystoliths, forms of, 210
cystoliths, occurrence of, 215
cystoliths, tests for, 215
hesperidin, 196
hesperidin, test for, 196
inulin, 194
inulin, tests for, 194
leucoplastids, 183
mucilage, 194
mucilage associated with raphides, tests for, 194
mucilage, tests for, 194
organic, 182
starch grains, formation of, 183
starch grains, hilum nature of, 188
starch grains, hilum of, 185
starch grains, mounting of, 188
starch grains, occurrence of, 184
starch grains, outline of, 185
starch grains, size of, 185
starch grains, tests for, 188
tannin, 196
tannin, occurrence of, 196
tannin, test for, 197
volatile oil, test for, 196
volatile oils, 196
Cell division common to onion root, 56
Cell plate, 55
Cell sap, 53
Cell, typical, 53
Cell wall, 53
Chromatin, 54
Chromatin granules, 55
Chromatophores, 53
Chromosomes, 55
Closed collateral bundles of mandrake stem, cross-section
illustration of, 296
Collateral vascular bundles, 295
Collenchyma cells, composition of walls, 109
illustrations, 108
occurring in catnip and motherwort, illustrations, 107
of ruellia stem, 235
structure of, 106
Compound microscope, illustration, 10
microscope, mechanical parts of, 7, 8
microscope of Robert Hooke, illustration, 8
microscope, optical parts of, 9, 11, 12
microscopes, introduction, 7
Concentric vascular bundles, 295
Conducting tissue, introduction, 126
Cork cells, origin of, 88
Cortical parenchyma, conduction by, 147
of ruellia stem, 235
Cortex, of pink root, 219
of ruellia rhizome, 226
of ruellia root, 221
of ruellia stem, 235
of spigelia rhizome, 223
of spigelia stem, 233
Cover glasses, 43
illustrations, 44
Crystal cavities, 176
cells, storage function of, 179
Cutting sections, 31
Cystoliths, illustrations of, 214
Cytoplasm, 53
Daisies, white, powdered, description of, 282
illustration of, 283
Dissecting microscope, illustration, 5
needles, 46
needles, illustration, 46
Drawing apparatus, illustration, 23
Ectoplast, 53
Embryo, diagnostic structures of, 291
Endocarp of celery fruit, 288
Endodermal cells, illustrations of longitudinal sections, 119
illustrations of cross-sections, 117
introduction, 116
structure of, 116, 118
Endodermis, of klip buchu leaf, 262
of pink root, 219
of ruellia root, 223
Endosperm of celery fruit, 288
of seeds, 291
Epicarp of celery fruit, 285
Epidermal cells of leaves, storage function of, 179
Epidermis, surface deposits of, 62
of herbaceous stems, illustrations of, 152
of klip buchu leaf, 260
of leaves, illustrations of, 155
of mountain laurel, 264
of pink root, 219
of ruellia rhizome, 226
of ruellia root, 221
of ruellia stem, 235
of seeds, 289
of spigelia rhizome, 223
of spigelia stem, 233
of testa, 63
Epidermis of trailing arbutus, 264
Equatorial plane, 55
plate, 55
Fibro-vascular bundles, composition of, 292
of klip buchu leaf, 262
types of, 292
Flowers, diagnostic structures of, 284
parts of, 270
Folding magnifier, 4
illustration, 4
Fruits, cellular structure of, 285
diagnostic characteristics of, 288
diagnostic structures of, 288
Glandular hairs of peppermint, 178
illustrations of, 165
multicellular, 164
multicellular, multiseriate stalked, 166
multicellular, multiseriate stalked, description of, 166
multicellular, multiseriate stalked, occurrence, 166
multicellular sessile, 164
multicellular stalked, 164
multicellular, uniseriate stalked, 164
stalked, illustrations of, 167
storage function of, 178
unicellular, 164
unicellular, multiseriate stalked, 164
unicellular sessile, 164
unicellular stalked, 164
unicellular, uniseriate stalked, 164
Glandular tissue, introduction, 164
Glass slides, 44
illustrations, 44
Greenough binocular microscope, 15
illustration, 15
Guard cells, 151
Hairs, multicellular, multicellular non-branched, illustration, 75
multicellular, multiseriate branched, of Shepherdia, 78
multicellular, multiseriate branched, 77, 82
multicellular, multiseriate branched, illustrations, 79, 81
multicellular, multiseriate non-branched, 74
multicellular, uniseriate branched, illustration, 76
multicellular, uniseriate non-branched, 72
multicellular, uniseriate non-branched, illustrations of, 73
Hand cylinder microtome, illustration, 34
microtome, 31
microtome, illustration, 31
table microtome, 34
table microtome, illustration, 34
Horehound, powdered, description of, 237
powdered, illustration of, 238
spurious, powdered, description of, 237
spurious, powdered, illustration of, 239
Hypoderm of seeds, 289
Hypodermal cells, of leaves, storage function of, 179
illustrations, 120
structure of, 118
Hypoderms, of klip buchu leaf, 260
of ruellia root, 221
Illumination for microscope, 26
Indirect cell division, 54, 55
Inner bark of white pine, 248
epidermis of seeds, 291
Insect flower leaves, powdered, illustrations of, 268
stems, description of, 241
stems, powdered, illustration of, 240
Insect flowers, closed, powdered, illustration of, 279
open, description of, 280
open, powdered, illustration of, 281
powdered, description of, 278
Intercellular spaces, 158
illustrations of, 160, 161
Internal phloem, of spigelia stem, 235
Inulin, illustrations of, 195
Karyokinesis, 54, 55
Klip buchu, cross-section, illustration of, 261
powdered, description of, 262
powdered, illustration of, 263
Labeling, 47
Latex cavities, 176
tube cavities, 176
tubes, 142, 144
tubes, illustration of, 145
vessels, illustrations of, 146
Leaf epidermis, 59
illustrations, 60, 61
Leaf parenchyma, conduction by, 150
Leaves, diagnostic structures of, 267
stomata, 260
Lenticel, illustration of cross-section, 159
Lenticels, ærating function of, 157
structure of, 158
Linin, 54
Long paraffin process, 29
Machine microtomes, 32
Measuring cylinder, 40
illustration, 40
Mechanical stage, 21
stage, illustration, 22
tissue, 89
Medullary ray, 139
bundle, 139
bundle in tangential-section of quassia wood, 258
cell, 141
cell, arrangement of, in the ray, 142
cell, structure of, 142
cells, in cross-section of quassia wood, 254
cells, in radial-section of quassia wood, 258
cells, in tangential-section of quassia wood, 258
cells, of ruellia stem, 237
Medullary rays, illustration of cross-sections of, 143
illustration of longitudinal section, 140
in cross-section of quassia wood, 254
in radial-section of quassia wood, 254
of pink root, 221
of ruellia rhizome, 227
of ruellia root, 223
of spigelia rhizome, 226
of white pine bark, 250
Mesocarp of celery fruit, 285
Method of mounting specimens, 41
Micro-crystals, illustrations of, 201
lamp, 27
Micrometer eye-pieces, 21
illustrations, 20, 21
Microphotographic apparatus, 24
illustration, 24
Microscope, how to use, 25
Microscopic measurements, 19
Microtome, care of, 36
Middle bark of white pine, 248
lamella, 55
layers of seeds, 291
Minor rotary microtome, 36
illustration, 36
Mountain laurel, cross-section, illustration of, 265
Mucilage cavities, 172, 176
Multicellular hair, 72
Nuclear membrane, 55
spindle, 55
Nucleoli, 55
Nucleus, 53
Objectives, illustrations, 11
Ocular micrometer, 19
illustration, 19
Oil cavities, occurrence, 178
of leaves, 178
of seeds, 178
unicellular, 172
Open collateral vascular bundles, description of, 298
Origin of multicellular plants, 57
Outer bark of white pine, 248
Palisade parenchyma, conduction by, 150
Papillæ, 67
illustrations of, 275
of stigmas, illustrations of, 276, 277
stigma, description of, 274
Paraffin, blocks, 31
embedding oven, illustration, 30
Parenchyma, aquatic plant, 150
cells of white pine, 248
conduction by, 144
cortical, illustrations of, 148
of mountain laurel, 264
of trailing arbutus, 264
pith, illustrations of, 149
Pericycle of pink root, 221
of ruellia root, 223
Periderm, 80
cork, 80
illustrations of, 86
of cascara sagrada, illustrations, 84
of white oak bark, illustration of, 87
parenchyma and stone cells, 85
stone cells, 85
Permanent mounts, 41
Pharmacognostic microscope, illustration, 12
Phloem, centric bundle of calamus, cross-section, illustration of,
294
of ruellia rhizome, 226
of ruellia stem, 235
of spigelia rhizome, 223
of spigelia stem, 233
Phloem parenchyma, conduction by, 150
of pink root, 221
of ruellia rhizome, 226
of ruellia root, 223
of ruellia stem, 235
of spigelia rhizome, 223
of spigelia stem, 235
Photosynthetic tissue, 163
Pink root, description of, 227
Pith parenchyma, conduction by, 147
of pink root, 221
of ruellia rhizome, 227
of ruellia root, 223
of ruellia stem, 237
of spigelia rhizome, 226
of spigelia stem, 235
Pitted vessels, with bordered pores, illustration of, 135
illustrations of, 134
Plant hairs, forms of, 67
introduction, 66
Polar caps, 55
Polarization microscope, 16
illustration, 16
Pollen grains, 270
non-spiny-walled, description of, 273
smooth-walled, illustrations of, 271
spiny-walled, description of, 273
spiny-walled, illustrations of, 272
Preparation of specimens for cutting, 28
Protoplast, 53
Quassia wood, cross-section, illustration of, 255
radial-section, illustration of, 257
Radial vascular bundles, 292
skunk cabbage root, cross-section, illustration of, 293
Raphides, illustrations of, 203
Reading glass, 4
illustration, 4
Reagent set, illustration, 39
Reagents, list of, 38
Research microscope, 13
illustration, 14
Reserve cellulose, illustrations of, 180-181
Reticulate vessels, illustrations of, 133
Root hairs, 121, 122, 125
illustration of, 123
illustration of fragments, 124
Roots and rhizomes, 219
diagnostic structures of, 227
Rosette and solitary crystals, illustrations of, 213
crystals, illustrations of, 204
crystals, inclosed, illustrations of, 206
Ruellia ciliosa, Pursh., powdered, illustration of, 229
ciliosa, Pursh., rhizome, cross-section, illustration of, 225
ciliosa, Pursh., stem, cross-section, illustration of, 236
root, description of, 227
root, illustration of, 222
Scalpels, 46
illustration, 47
Scissors, 46
illustration, 46
Sclariform vessels, illustrations of, 132
Seeds, parts of, 289
Secretion cavities, of celery fruit, 288
description of, 176
illustrations of, 169-171
introduction, 166
lysigenous, 168
schizogenous, 168
schizo-lysigenous, 168
unicellular, 168
Secretion cells, of klip buchu leaf, 262
of white pine, 248
Short paraffin process, 29
Sieve cells, of klip buchu leaf, 262
of pink root, 221
of ruellia rhizome, 226
of ruellia root, 223
of ruellia stem, 235
of spigelia stem, 235
Sieve plate, 138
illustration of, 137
Sieve tube, illustration of, 137
tubes, introduction, 136
tubes, structure, 136
Simple microscope, introduction, 3
Slide box, 48
box, illustration, 48
cabinet, 49
cabinet, illustration of, 49
forceps, 45
forceps, illustrations, 45
tray, 48
tray, illustration, 48
Solitary crystals, illustrations of, 207-209, 211, 212
unicellular hairs, 69
Special research microscope, 14
illustration, 14
Specimens, preservation of, 48
Spermoderm, of celery fruit, 288
of seeds, 289
Spigelia marylandica, powdered, illustration of, 228
rhizome, cross-section, illustration of, 224
root, cross-section, illustration of, 220
stem, cross-section, illustration of, 234
Spindle fibres, 55
Spiral vessels, illustrations of, 129, 130
Spongy parenchyma of klip buchu, 260
Stage micrometer, 19
illustration, 19
Staining dish, 40
illustration, 40
Standardization of ocular micrometer, 19
Starch grains, illustrations of, 186, 187, 189-193
Steinheil lens, 5
illustration, 5
Stems, diagnostic structures of, 233
dicotyledonous, 233
herbaceous, 233
monocotyledonous, 233
Stomata, ærating function of, 151
illustrations of cross-section, 156
relation to surrounding cells, 154
types of, 153
Stone cells, of ruellia root, 223
branched, 109
branched, illustrations of, 110
description, in, 112
introduction, 109
occurrence, illustrations, 115
porous and non-striated, 111
porous and non-striated, illustrations of, 114
porous and striated, 109
porous and striated, illustrations of, 113
storage function of, 178
Storage cavities, 176
cavities, illustrations of, 177
cells, 173
cells, cortical parenchyma, 173
cells, illustrations of, 174
cells, pith parenchyma, 173
cells, wood parenchyma, 173
tissue, 173
walls, description of, 179
Stored mucilage and resin, illustrations of, 175
Surrounding cells, arrangement of, 154
Synthetic tissue, introduction, 163
Temporary mounts, 41
Testa cells, 65
epidermal cells, illustrations, 64
Tracheids of pink root, 221
Trailing arbutus leaf, cross-section, illustration of, 266
Tripod magnifier, 4
illustration, 4
Turntable, 46
illustration, 47
Under epidermis of klip buchu leaf, 262
epidermis of mountain laurel, 264
of trailing arbutus, 264
hypodermis of klip buchu leaf, 262
palisade parenchyma of klip buchu leaf, 262
Unicellular clustered hairs, 72
clustered hairs, illustrations, 71
non-glandular hairs, 69
solitary branched hairs, 72
solitary hairs, illustrations, 70
Upper palisade parenchyma of klip buchu leaf, 260
palisade parenchyma of mountain laurel, 264
Vacuoles, 53
Vascular bundles, arrangement of, 292
occurrence of, 292
Vessels, annular, 127
and tracheids, introduction, 126
in cross-section of quassia wood, 254
in radial-section of quassia wood, 254
in tangential-section of quassia wood, 258
of ruellia rhizome, 226
of ruellia root, 223
of ruellia stem, 237
of spigelia rhizome, 226
pitted, 131
pitted with bordered pores, 131
reticulate, 131
sclariform, 128
spiral, 127
Water pores, aerating function of, 151
Watchmaker’s loupe, 4
illustration, 4
Wood fibres, color of, 104
illustrations, 105
in cross-section of quassia wood, 254
in radial-section of quassia wood, 258
in tangential-section of quassia wood, 258
introduction, 104
structure of, 104
Wood parenchyma, conduction by, 150
in cross-section of quassia wood, 254
in radial-section of quassia wood, 258
of pink root, 221
of ruellia rhizome, 227
of ruellia root, 223
of ruellia stem, 237
of spigelia rhizome, 226
of spigelia stem, 235
Woods, description of, 254
diagnostic structures of, 258
Woody stems, buchu stem, description of, 242
mature buchu stem, 242
Xylem, of pink root, 221
of ruellia rhizome, 226
of ruellia root, 223
of ruellia stem, 237
of spigelia rhizome, 226
of spigelia stem, 235
Transcriber’s Notes
The Table of Illustrations at the beginning of the book was created
by the transcriber.
Inconsistencies in hyphenation such as
“extra-ordinary”/“extraordinary” have been maintained.
Minor punctuation and spelling errors have been silently corrected
and, except for those changes noted below, all misspellings in the
text, especially in dialogue, and inconsistent or archaic usage,
have been retained.
Page 53: “The outer portion of the nucelus” changed to “The outer
portion of the nucleus”.
Page 54: “the centre of the nucelus” changed to “the centre of the
nucleus”.
Page 62: “typical forms of arrangement of epidermal calls” changed
to “typical forms of arrangement of epidermal cells”.
Page 104: “of logwood and santalum rubum” changed to “of logwood
and santalum rubrum”.
Page 107: “the cross-section of catnip stem (_Nepeta cateria_”
changed to “the cross-section of catnip stem (_Nepeta cataria_”.
Page 120: “Cross-section sarsaparilla root (_Smilex officinalis_”
changed to “Cross-section sarsaparilla root (_Smilax officinalis_”.
Page 150: “cells are the narrowest parenchyma cells occuring”
changed to “cells are the narrowest parenchyma cells occurring”.
Page 155: “Upper epidermis of deer tongue (_Trilisia
odoratissima_” changed to “Upper epidermis of deer tongue
(_Trilisa odoratissima_”.
Page 171: “Parenchyma cells with protuding” changed to “Parenchyma
cells with protruding”.
Page 193: “grains of paradise (_Amomum meleguetta_” changed to
“grains of paradise (_Amomum melegueta_”.
Page 237: “Marrubium perigrinum, which is a related species of
horehound” changed to “Marrubium peregrinum, which is a related
species of horehound”.