NationalLibraryOfScotland/medical-history-of-british-india huggingface dataset:
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Scientific Memoirs by
The great majority of the roots show the peculiar appearance of being divid-
ed into zones or segments. Typically the whole root is marked off into zones
of approximately equal depth, the zones being alternately white and brown. Thus
a root measuring 3" long was divided off into fourteen practically equal segments
or zones. The segmented appearance is brought about really by the development
of the white zones, the brown zones being the ordinary epiblemal tissues, not
encroached upon by the white zones.
The white zones have the appearance as if the root had been ' ringed,' and
the ring then dusted with oatmeal or flour, according to the coarseness or fine-
ness of the appearance. The floury looking deposit is a good deal thicker at the
upper part of each white zone than at the lower. The upper edge of a white
zone is abrupt and irregular in outline, with torn fragments of epiblemal tissues
overhanging it. This lower edge is indefinite, fading away into the brown zone
below.
In the smaller roots at least, each white zone increases in diameter froth
below upwards and each brown zone from above downwards, so that at the junc-
tion of the upper margin of each white zone with the lower margin of the brown
zone above, the root shows a distinct nodal appearance.
There are, however, no true nodes present, so it is here preferred to consider
the root—figure 1 of Plate 1 , A,—taken as a typical example to be divided into
fourteen zones, seven white and seven brown, rather than into seven segments,
each showing an upper white and a lower brown division.
The typical arrangement above described is often departed from. The white
zones may be at quite irregular distances from each other, separated often by a
considerable length of ordinary looking root. Instead of a white zone entirely
surrounding the root, there may be only an irregular shaped floury patch on one
side of the root.
These white zones or patches are absent from the lower parts of the roots,
sunk well into the mud, and from those parts of the branch roots below the sur-
face.
The young roots are white in colour, but as they grow older and firmer, they
assume gradually deeper tints of brown, till ultimately they are almost black.
In studying the anatomy of the root, hand-cut sections were made use of.
For reagents, caustic potash, iodine, and strong sulphuric acid were employed.
Safranin was used for staining, sometimes contrasted with Hoffmann's Blue. The
sections were usually mounted in glycerine, sometimes in Canada balsam.
A transverse section through a brown zone, examined under a magnification
of eight diameters, shows the appearance represented in figure I of Plate II. In
Fi g. 2 X 8/1
Fig. 10 X 340/1
PLATE II
Fig. 3 X 340/1
Fig. 5 X 340/1
F i g . 6 X 3 4 0 / 1
Fig. 9 X
73/1
Fig. 7 X 340/1
Fi g. 8 X 73/ 1
A. T. G. del.
PHOENIX PALUDOSA Roxb.
EXPLANATION OF PLATE II.
Fig. I. Transverse section of medium sized root of Phœnix paludosa Roxb., taken
through a brown zone. Magnification 8 diameters.
B. Outer hypodermal ring.
C. Inner hypodermal ring.
D. Cortex with numerous strands of sclerenchyma cut across.
E. Ring of cortical tissue just exterior to the endodermis.
F. The endodermis, represented as a single black line.
G. Ring of fibro-vascular bundles.
H. Ring of sclerenchyma, with one or two reticulated ducts in it.
K. Pith showing two columns of sclerenchyma cut across, each surrounding a
reticulated duct.
Fig. 2 . The same in longitudinal section. The letters refer to the same regions as in
figure I. Magnification 8 diameters.
Fig. 3. Transverse section through outer portion of young root.
A. Epiblema.
B. Hypodermal tissue. Magnified 340 diameters.
Fig. 4. Transverse section of the same region as in figure 3, but in an older root,
showing the differentiation of tissue that has taken place.
B. Outer hypodermal ring.
C. Inner hypodermal ring. The two rings of tissue are here separated by
a band of thin walled tissue. Magnified 34o diameters.
Fig. 5. Longitudinal section of outer hypodermal ring.
B. As above. Magnified 340 diameters.
Fig. 6. Longitudinal section of cells from the inner hypodermal layer C. Magnified 340
diameters.
Fig. 7. Transverse section of a strand of sclerenchyma from region D of the cortex
surrounded by cortical cells. Magnified 340 diameters.
Fig. 8. An isolated sclerenchymatous cell from one of the strands of sclerenchyma in
the inner region of the cortex. Magnified 73 diameters.
Fig. 9. Longitudinal section of cells from the same region of the cortex, showing the
peculiar secretory (?) cells with dark contents. Magnified 73 diameters.
Fig. 10. Longitudinal section of cells from the same region. Magnified 340 diameters.
Medical Officers of the Army of India.
1 0 5
the centre of the section is the stele, which occupies about a quarter of the whole
diameter of the section. The stele is surrounded by a thick cortex, showing a
division into four or five distinct regions. The cortex, in the young root at least,
is surrounded by the epiblema, which cannot, however, be made out distinctly
under this low power.
Beneath the epiblema lies the outermost division of the cortex, built up of
very small closely packed cells, B of figures 1 and 2 of Plate II.
Within this comes a clear ring of cells with unthickened walls, not represented
in figures 1 and2 ,
b u t s e e n u n d e r a h i g h p o w e r i n f i g u r e 4 , t a k e n f r o m a n o t h e r
section.
Next comes another band of closely packed cells, not so small as those of
the outer band. This band—C of figures 1 and 2 o f P l a t e I I — i s r e f e r r e d t o
throughout this paper as the inner hypodermal ring to distinguish it from the
outer band B, called here the outer hypodermal ring.
Within the inner hypodermal ring C, lies the greater portion of the cortex D
of figures 1 and2 o f P l a t e I I . E v e n u n d e r t h i s l o w m a g n i f i c a t i o n t h i s r e g i o n o f
the cortex is easily seen to be built up of loose cellular tissue, with numerous
comparatively large spindle shaped intercellular spaces, which exhibit a radial
arrangement.
Scattered thickly throughout this region are small, more or less circular or
oval, islands of lignifled tissue, represented as black dots in figures 1 and 2 o f
Plate II. They are in reality, as shown in figure 2, transverse sections of strands
of sclerenchyma.
The innermost region of the cortex E, in figures 1 and2 o f P l a t e I I , f o r m s a
narrow ring of tissue immediately surrounding the endodermis and is built
up of oval radially compressed cells without intercellular spaces.
The endodermis surrounding the stele is seen as a thin line, represented too
thick in figure 2 of Plate II. Immediately within the endodermis is the clear ring
of tissue—G in figures 1 and2 o f P l a t e I I — i n w h i c h t h e x y l e m a n d p h l o e m b u n d l e s
lie. The xylem bundles alone are visible under this low power as black dots.
There are about thirty bundles in the ring. The small clear circles seen, one in-
ternal to each xylem bundle in figure 1 of Plate II, are the transverse sections of
thin walled reticulated ducts of comparatively large calibre.
Within the ring of xylem and phloem bundles is a broad band of compact thick
walled sclerenchyma. Several thin walled reticulated ducts are seen cut across in
this band, H of figures 1 and2 o f P l a t e I I .
Within this sclerenchymatous ring is the pith, which often shows imbedded in
it one strand or several strands of sclerenchyma, each surrounding a thin walled
reticulated duct.
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Examination of the various regions roughly indicated above in detail under
a high power gave the following results :
—
The epiblema in the young root is a single layer of thin walled and, in trans-
verse section, polygonal cells with clear contents. It can scarcely be distinguish
-ed from the underlying hypodermal tissue, except by the rather larger size of its
cells. The average radial diameter of its cells is 11 . 5u , average tangential dia-
meter 15
u
.
As seen in figure 3 of Plate II, the cells forming the two or three layers
beneath the epiblema are little inferior in size to the epiblemal cells. The succeed-
ing four or five layers are built up of smaller cells, which afterwards develop
secondary thickening on their walls, and form the outermost layers of the root,
when the epiblema and its immediately underlying cells have been thrown off.
These four or five layers form a band of thick walled tissue, which is referred to
throughout this paper as the outer hypodermal ring, B of figures I, 2, and 4 of
Plate II.
To the inner or central side of this outer hypodermal ring are five or six
layers of clear thin walled cells, forming a clear ring between the outer hypodermal
ring B and the inner hypodermal ring C. It is well seen in figure 4 of Plate II.
The inner hypodermal ring C is built up of large polygonal cells, which
soon develop thickenings on their walls.
The ring is about eight layers of cells in breadth, and is continuous centrally,
with the outer cells of the region D of the cortex.
As the root develops the walls of the cells of the outer hypodermal ring be-
come thickened.
The outermost layer or the two outermost layers become cuticularised and
show obscure striation.
The epiblema and its immediately underlying two or three layers of cells thus
cut off from food supply wither away. The outermost layer of cells of the outer
hypodermal ring then takes the place of the epiblema, and may simulate it very
closely, and if the two outermost layers have been cuticularised, they look remark-
ably like a two-layered epiblema. The ragged remains of the true epiblema and
underlying unthickened cells, occasionally seen adhering to the outermost layer of
the outer hypodermal ring, show the true state of affairs. In figures 4 and 5 of
Plate II the true epiblema and underlying cells have disappeared.
The radial diameter of the cells of the outer hypodermal ring varies from 6
u
to 15u . the tangential practically the same.
In longitudinal section the cells of the outer hypodermal ring are oblong in
outline, with a diameter varying from 30 u to 60
u
.
The small u given after the figures of the dimensions of cells signifies micromillimetres.
Medical Officers of the Army of India.
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The inner layers of this ring appear to be developed successively from
the outer cells of the clear ring separating the outer hypodermal ring from the
inner. The clear ring may be reduced to a single layer of cells separating the
two sclerenchymatous rings, or all its cells may undergo secondary thickening, so
that the outer and inner hypodermal rings become continuous. In longitudinal
section the cells of this clear ring resemble those of the outer hypodermal ring,
but with thin walls.
The inner hypodermal ring in cross section is built up of about six layers of
large polygonal cells, with secondary thickening and many narrow pits. The
radial diameter of the cells varies roughly from 26
u
to 44u. Their length varies
from 44
u
to 300
u
. They are oblong in longitudinal section, with rounded
ends. The appearance of the cells is shown in figures 4 and 6 of Plate II.
Within this inner sclerenchymatous ring is the greater part of the cortex,
marked D in Plate II. The cells of this region are more or less circular, or some-
what polygonal, in outline in transverse section, with numerous intercellular
spaces and unthickened walls. Their diameter varies from about 23
u
to 64
u
measured in the transverse section.
Many of the cells present the peculiar appearance of having each a smaller
cell inside, the real cell and the apparently contained cell, looking like two con-
centric circles, as seen in figure 7 of Plate II. A longitudinal section explains
the appearance. In longitudinal section the cells are markedly polygonal.
At every intercellular angle the combined wall forming the partition between
contiguous cells, splits, so as to enclose a small circular or oval or triangular
space. This space is very distinctly marked off in sections mounted in glycerine
by the clear cut, swollen, and hyaline appearance of its bounding walls, in con-
trast to the dark granular looking walls common to the cells where they remain
in contact. The appearance is seen well in figure 10 of Plate II. This peculiar
appearance as of small hyaline cells interpolated at each intercellular angle is
not nearly so well marked in sections mounted in Canada Balsam. In transverse
section it frequently happens that one of those clearly bounded circular spaces
is in practically the same focus as the section of the cell at the basal or apical
angle of which it is situated, so that the intercellular space appears as a circular
cell inside the large cell. The same appearance is seen also in longitudinal
section, though not so markedly.
Scattered amongst the ordinary cortical cells are somewhat larger ones,
which show dense contents, sometimes faintly granular, at other times resinous
or gummy looking in appearance.
cc
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The contents contract slightly in material treated with alcohol, and very
readily take up the safranin stain, in marked contrast to the surrounding cells, which
prefer the Hoffmann's Blue. None of the reagents at the writer's disposal had
any effect on the cell contents. Probably these large cells are secretory in func-
tion. Their appearance and relative frequency to the ordinary cortical cells is
seen in figure 9 of Plate II.
The longitudinal diameter of an ordinary cortical cell is about 46 u.
Towards the periphery the cortical cells become smaller in transverse section
and more oblong in longitudinal section, and the intercellular spaces disappear.
They gradually merge into the inner cells of the inner hypodermal ring. Central-
ly the cortical cells form a distinct band, E of figures 1 and 2 of Plates II and
III, immediately surrounding the endodermis. The cells of this band are oval
in transverse section, and radially compressed.
Their radial diameter varies from about 8u to about 16u, their tangential
diameter from about 15u to about 45u.
In longitudinal section they are oblong, with a diameter varying from about
38 u to about 82u . There are no intercellular spaces and the cell walls are
rather thick and coarsely granular in appearance.
The large spindle shaped intercellular spaces appear to be formed by the
chizogenous separation of one or more radial rows of cells, which cells at first
lie loose, and ultimately break down and disappear.
The strands of sclerenchymatous tissue, scattered thickly through the
cortex are polygonal, or more or less circular, in transverse section, and are built
up of about thirty to forty cells at any one level. Longitudinally they run in
straight parallel columns. The individual cells are spindle shaped, about 6 mm.
long and 5 . 5u broad.
The endodermis surrounding the stele is a single layer of cells, which at first
are thin-walled, and square in transverse section. Soon, however, secondary thick-
enings are laid down on their central and radial walls, reducing the lumen
very considerably. The secondary thickening is not laid down uniformly, but
leaves pits, looking like small canals traversing the thickened cell wall. The
appearance of the endodermis when secondary thickening has occurred is seen
in figure I of Plate III. Passage cells with unthickened walls are left here and
there in the ring, either solitary or three or four in a row. The average radial
diameter of the cells is 15u, the tangential 18 u and the longitudinal 60 u.
Internal to the endodermis is the pericycle, P of figures 1 and 2 o f P l a t e I I I ,
consisting of a single layer of thin-walled cells rather larger than the cells
of the endodermis, with which they alternate, and oval or polygonal in outline.
EXPLANATION OF PLATE III.
Fig. 1. Transverse section of portion of stele.
E. Inner cells of cortex.
F. Endodermis, with well marked secondary thickening of its cell walls.
P. Pericycle.
X X. Xylem bundles.
Ph. Phloem bundle.
R. D. Large reticulated duct.
H. Band of sclerenchyma surrounding the pith.
Magnification 340 diameters.
Fig. 2. Longitudinal section of portion of stele.
The letters have the same significance as in fig. 1.
The cells between the large reticulated duct and the sclerenchymatous ring
are omitted. Magnification 340 diameters.
Fig. 3. An isolated cell from the sclerenchymatous band H. Magnification 73
diameters.
Fig. 4. Transverse section through a root to show origin of a white zone, taken just
above a white zone. The letters B, C, D, E, F, G, H, K have the same
significance as in former figures.
Ca. The layer of outer cortical cells, which are in active division, giving rise
to the cells forming the white zone.
Pc. The mass of cells, giving the white mealy appearance, Magnification
8 diameters.
Fig 5. Longitudinal section to show the origin of a white zone, taken through the
junction of a white zone with the brown zone above.
The letters have the same significance as in fig. 4.
The appearance of the dark band just external to Ca. in figs. 4 and 5 is due to
the presence of air, which could not be dislodged.
Fig. 6. Transverse section through the actively dividing layers marked Ca. in figs. 4
and 5. Magnification 115 diameters.
Cor. Outer cortical cells.
Ca. Actively dividing layers of cells.
Pc. The cells of the white zone.
Fig. 7. Cells from the white mealy zone Pc. Magnified 340 diameters.
Fig. 8. Crystals of calcium oxalate from the cortical cells. Magnified 340 diameters.
Fig. 9. Longitudinal section through tip of root, showing growing point and root cap.
Significance of letters as befor. Magnified 8 diameters.
PLATE III.
Medical Officers of the Army of India.
109.
Their radial transverse diameter varies from 8
u
to about 16
u
, their tangential
from 12 u to about 2 3
u
. Longitudinally they are polygonal, with a longitudinal
diameter varying from about 32
u
to about 66
u
.
The xylem bundles are separated from the pericycle by a single layer of
thin-walled cells, which are smaller than those of the pericycle. A xylem
bundle is built up of about six reticulated or practically scalariform vessels,
polygonal in transverse section and of diameter varying from about 5
u
to about
24
u
. The largest vessel is almost always nearest the centre of the root. The
surrounding unlignified cells are polygonal in transverse section, varying a good
deal in size, elongated longitudinally with pointed ends.
To the-inner side of each xylem bundle, and separated from it by one or
two layers of unlignified cells is a large thin-walled reticulated duct, almost
circular in transverse section. Its elements measure about .8 mm. in length.
Alternating with the xylem bundles are the phloem bundles, made up of
the usual elements. Each bundle shows from four to six somewhat large empty
cells, the sieve tubes cut across, situated towards the centre of the root. Between
those and the pericycle and also surrounding them to some extent are the small
companion cells, with densely stained contents.
The length of the elements making up a sieve tube varies from 75
u
to about
200 u.
Within the ring of xylem and phloem bundles, between it and the pith, is
a broad band of sclerenchymatous cells, about eight to twelve layers in breadth.
It is separated by one or two layers of thin walled cells from the large reticu-
-lated ducts situated to the inner side of the xylem bundles. It usually shows
rays projecting outwards between those large ducts. Sometimes there is present
a second more or less complete circle of large thin walled ducts, situated nearer
the centre of the stem than those opposite the xylem bundles. The ducts of
this inner circle may get completely surrounded by the rays sent out from the
sclerenchymatous band, and they then appear to be imbedded in the
scleren-chymatous band. This inner circle may be reduced to only one or two ducts.
Each duct is immediately surrounded by a layer of thin walled cells. The
cells of this sclerenchymatous band are polygonal in transverse section, with
a diameter varying from about 8
u
to about 32
u
. The secondary thickening is
not uniform, for many pits are left. In longitudinal section the cells are spindle
shaped, with an average longitudinal diameter of .7 mm.
The pith, which is surrounded by this sclerenchymatous band, is composed
of cells similar to those of the cortex, having the same appearance in transverse
Scientific Memoirs by
section, and in longitudinal section differing only in the greater length of the
cells.
The transverse diameter varies from 20" to about 67", the longitudinal
from 36" to 92". The intercellular spaces show the same peculiar appearance
as in the cortex. There are also present the same kind of large secretory (?)
cells, with dark staining contents, as in the cortex.
Sections taken through a white zone of a root show, so far as the greater part
of the cortex and the stele are concerned, the same structure as sections through a
brown zone.
There is, however, a considerable difference in the outer cortical region, which
may best be explained by tracing the course of development that leads to the
appearance of the white zones.
In the region of the root, where a white zone is about to develop, the inner
sclerenchymatous hypodermal ring is absent. The outer cells of the cortex in the
region, corresponding to the inner margin of the inner hypodermal ring, form
several layers of actively dividing cells. These cells are thin walled, oval or
circular, and continuous internally with the ordinary cortical cells. Externally
these actively dividing layers of cells produce a crescentic mass of cells, the
inner three or four layers of which are made up of cells also in a state of sub
-division and of the same shape as the cells of the underlying originating layers,
only with thicker and coarser walls. As the cells of the mass are pushed further
out, they develop large intercellular spaces and assume very irregular shapes,
as shown in figure 7 of Plate III. Under a high power they are seen to be finely
muriculate. The whole mass reminds one of the packing cells of a lenticel.
The crescentic mass of packing cells is at first bounded externally by the
outer hypodermal ring, and at each horn of the crescent by the ends of the in-
complete inner hypodermal ring. Ultimately the pressure of the mass of rapidly
formed cells increases to such an extent that the outer hypodermal ring, and
overlying epiblema if present, are ruptured, and the mass of cells appears on the
surface as a white patch.
The above description applies to the appearance of a transverse section
taken just a little above the upper margin of a white zone, and represented in
figure 4 of Plate III.
A transverse section taken just below the upper margin of a white zone,
shows the layers of actively dividing cortical cells encircling the entire circum-
ference of the root and giving off packing cells all round, which externally are
separating from each other and falling away. There is no trace of the inner
hypodermal ring.
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