The Structure of the Wall of the Green Alga Valonia ventricosa
Author(s): R. D. Preston and W. T. Astbury
Source: Proceedings of the Royal Society of London. Series B, Biological Sciences, Vol. 122, No.
826 (Mar. 3, 1937), pp. 76-97
Published by: The Royal Society
Stable URL: http://www.jstor.org/stable/82132
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Valonia
576.3J4:5^2.266.1
The
the
of
Structure
Valonia
By
R. D. Preston
{Communicated
and
of
Wall
the
Green
Alga
ventricosa
W. T. Astbury,
of Leeds
University
by Sir William
Bragg, O.M.,
21 October 1936)
P.R.S.?Received
1, 2]
[Plates
Introduction
for many years the study of cytology
has tended to concentrate
as the fundamental
unit of the
more and more on the protoplast
Although
attention
plant,
there
can
be no doubt
that
the
membrane
this unit
surrounding
in its life processes.
The deposition
is as yet quite obscure, is obviously
importance
plays a part of considerable
of such a membrane,
by a process which
with protoplasmic
activity,
closely connected
of its structure
At the same
to the
action
is bound
to lead to a better
and a detailed
understanding
and size of a cell are clearly
time, the shape
of forces external
and internal
investigation
of this connexion.
due in some degree
so that a
on the membrane,
wall should therefore
of the plant cell
also yield
study of the structure
information
of considerable
in
the
solution
of
botanical
importance
prob?
with cell elongation
lems concerned
and growth.
recent
Comparatively
carried out chiefly
on plant fibres, have shown that the
investigations,
of cell walls, from a structural
most important
component
point of view,
is the polysaccharide
cellulose.
This substance
is known to occur in varying
in the walls of almost all plant tissue and its structure
has been
proportions
worked
with some degree of
out, chiefly by X-ray and chemical
methods,
much
to
be
remains
discovered
of
the organization
of
certainty.
Although
cellulose in the wall, certain details are now quite clear. Celluloses
obtained
from many and varied plant sources have all proved to have essentially
the
same structure.
They exist only in the form of chains of /?-glucose residues,
500 A long (Hengstenberg
and Mark 1928), bound together
laterally
to
form
a
valences
three-dimensional
lattice.
The conception
by secondary
of a definite micelle, in the sense of Nageli,is
no longer widely held, although
the lattice
is not uniformly
the wall. The chains
of
regular throughout
at least
cellulose
are
separated
by regions
more
probably
in which
bound
they
into
ill-defined
together
are not so perfectly
oriented.
76
[
]
bundles
The
of Valonia
Wall
ventricosa
of cellulose
of the existence
This conception
of the secondary
from the examination
arisen
no direct
in primary
Carey and
determinations
experimental
walls where
have
77
in long molecular
chains has
walls of plants,
but as yet
been possible
of its structure
it is known
to occur (e.g. in
Recent
work (Preston
Priestley
1922).
of the conifer, however,
show that it is possible
to
the long-chain
even to these
structure
of cellulose
see TupperViciafaba,
1934) on the tracheids
carry over the idea of
delicate
walls.
primary
the
same
struc?
essentially
with
distribution
of cellulose
This widespread
ture makes it possible to generalize
results obtained
on the wall of one type
of cell to cover that of many other types, and it is from this point of view
that the work described
below will be of interest to botanists.
It is possible
to make
on the
observations
make
technique
of
large cells of Valonia which imperfections
with the minute
cells of the higher
plant.
impossible
observation
of the structure
of the whole wall, which
on large cells such as this alga affords, will probably
on the problems
involved
in the
bearing
yield results with an important
cellulose
wall
at
the
of the
surface.
protoplasmic
deposition
accurate
Moreover,
can be made only
of the Siphonales
(Fritsch
1935) characterized
by
cells, which in some species may be two or three centimetres
in apparently
seas, sometimes
long and which are found in the warmer
and
in
the
neat
sometimes
form
of
clusters
Of the three
palisades.
irregular
and V. macrophysa
V. ventricosa
form
species used in this investigation,
is a member
Valonia
its bubble-like
or pear-shaped
cells which in the former generally
occur
than
the
of
cells
V.
while
larger
proliferating
macrophysa;
close
clusters
of
cells
which
are
proliferates
freely giving
spherical
usually
singly,
being
V. utricularis
smaller
and frequently
somewhat
relatively
below has been carried
work to be described
observations
sufficient
their
cell-wall
A brief
account
that
in the first paper
becomes necessary
is based
made
have
been
made
structure
is essentially
similar.
of the morphology
of the alga
of this
series
(Astbury,
Marwick
Valonia
has been
and Bernal
here to enlarge upon this outline.
(1922) and Fritsch (1935)^0
details. The cell may be imagined
with a large vacuole
approximately
spherical,
Imbedded
in this lining are to be found numerous
away against the cell wall occur the chromatophores,
of irregular
given
but it
whom
while
nuclei,
in the form
plasm.
further
of plates
1932),
The following summary
reference
may be
as a large bubble, often
and a thin lining of proto?
on Oltmanns
for further
The bulk of the
elongated.
out on V. ventricosa,
although
on the other two species to show
outline
The
often
united
to form a network
is in turn
containing
pyrenoids.
protoplasmic
lining
rounded
thick wall, consisting
by a comparatively
and frequently
sur?
completely
chiefly
of cellulose.
R.
78
Valonia
vesicular
D.
Preston
and
T. Astbury
W.
with the protoplast
is a coenocytic
contained
in large
organism
cells, but minute cells are often formed as a result of accumula?
in certain regions of the surface.
A strongly
of protoplasm
curved
a
formed
like
is
round
such
masses
wall, shaped
watch-glass,
protoplasmic
This process gives two kinds
appearance.
giving a cell with a characteristic
of cells, larger ones which appear in the upper part of the cell, and smaller
tions
at the base. The latter grow out into short,
occur particularly
which form the holdfasts,
structures
but
while the larger
lobed,
single-celled
out
into
new
bubble-like
cells on the upper part grow
structures
which
ones
which
resemble
the
parent
in every
way,
including
the
power
of forming
new
cells.
of cells by the formation
The reproduction
of zoospores
has been closely
several
The
and
described
observed
of zooby
investigators.
propagation
several
days before their ejection
spores is made obvious
by the various
in the wall and protoplasm
of the mother cell
occurring
The
fertile
not
is
the rest of the
from
plasma
(Kuckuck
separated
1902).
for
as
it
in
wall
a
is,
Vaucheria,
etc., but the
example,
plasma by
Bryopsis,
with the outside
is in direct communication
vacuole
environment
at the
localized
time
changes
of spore ejection.
the wall is completely
to ejection,
closed up and the mother
cell
Previous
the
being subsequently
opening
There seems
to be no evidence
condition.
original
area of wall.
under
formation
takes place
any particular
no disturbances
in wall structure
have
research
present
its
as one would
a priori
expect
from
investigation
are closed up in such
In the course
regaining
this spore
in the
Certainly
that
been
found
in the membrane.
such
Either
openings
or the perfora?
produced
zoospores
as to leave no trace of their existence.
had never
the cell under
tions
such
pierced,
a way
of the work to be described
below
it has become
clear that
of the cells of Valonia
is strikingly
similar to that of the
fibres of the higher plant. The wall is laid down in microscopically
visible
be
as
as
which
or
in
and
the
crossed
number,
may
many
thirty
forty
layers,
chains
described
cellulose
are found,
as a result
of taking
previously
the wall structure
numerous
X-ray photographs
of chains traversing
sets
plete
one forms
of the same
the
whole
of two com?
cell, to be portions
wall surface.
Of these two sets
a left-hand
spiral round the cell, while the other takes the form
from
one pole of the spiral to the other.
At the two
running
the typical
of Valonia is
poles of the spiral, therefore,
X-ray photograph
no longer obtained,
being replaced
by a Debye-Scherrer
ring diagram.
of meridians
Moreover,
striations
layer.
these
two sets of chains
in the wall
The existence
to the microscopically
visible
correspond
in separate
in
rather
than
the
same
layers
striations
in different
had
been
layers
already
and occur
of the
The
of Valonia
Wall
ventricosa
79
(1892) and it has been verified during the
forward
by Sponsler
put
(1931) that the chains
present
about their axis, with the planes of 6* 1 A spacing
are definitely
oriented
true. The
always parallel to the wall, has been shown to be only roughly
but there is a considerable
chains do tend to lie in this position,
dispersion.
of Correns
in the work
indicated
research.
The view
due to the poles of the spiral, the only
Apart from the disturbances
occur at well-defined
of the wall structure
breaks in the regularity
places
At the holdfasts
been
formed.
and at the
where "watch-glass"
cells have
scar left by the falling off of a bud cell the wall undergoes
show a series of raised
region of the holdfasts
The
which
Yd mm. diameter
scope when illuminated
a crater-like
some modification.
circular
under
rims
some
the micro?
appearance
The two sets
to the wall surface.
parallel
with those outside
on the wall inside each rim are continuous
striations
present
of
it,
a rim gives a Debye-Scherrer
a piece of wall containing
ring
Bud scars have a
the
in
microcamera
(see Preston
diagram
X-ray
1934).
similar appearance,
though on a much larger scale.
although
and
Striations
Wall
Layers
in the first paper of this series a conclusive
demonstration
was
Although
the directions
of the striations
between
and
given of the correspondence
those of the cellulose
it may not be out of place here to enlarge
chains,
will serve in
The results
in this connexion
upon this point.
presented
to indicate
particular
between
the cellulose
on many pieces of Valonia
on the striations
case
was there observed
in
one
an
and
cells,
only
in
fold
the
in
for
a
wall
direction
unaccounted
discontinuity
by
reference
to this exceptional
will be made later). The
specimen
taken
obvious
(special
from
several
under the
can readily be observed
not
is
each
striation
of
wall,
equally
piece
although
the
and this necessarily
implies that the angle between
in direction
constancy
in any
microscope
visible at all points,
striations
must also
obtained
in the various
of precision
interrelations
and striations.
extinction
positions,
order
chains,
been made
have
Observations
wall
the
with
of the striations
have been
specimens
separate
from 60? to 80? or more, the
angles varying
This will
varies in a strikingly
gradual fashion.
be constant.
interstriation
While
angle in any one specimen
be clear from Table I, which gives a series of readings
on a single small
of which Table I
of
The
results
wall.
of
Valonia
piece
many measurements,
travel in
is a representative
that in general the striations
sample, indicate
lines
which
are to a close
approximation
straight
over a distance
of several
R.
80
D.
Preston
and
the
particular,
0-5
mm.)
(diameter
In
millimetres.
spectrometer
area
covered
a
b
'^ c
d
|
JJL e
84-4?
86-6?
86-0?
85-2?
84-2?
83-6?
81-6?
83-6?
81-6?
87-0?
76-0?
76-4?
83-0?
83-8?
78-4?
uniform
nature of the
remarkably
inner
structural
of
are
reflections
they
striations
This
that
was
used
determined
together
by
the
with
similar
the
a representative
was
striations
of this,
conclusively
and that the
them.
but
84-2?
85-0?
83-6?
85-4?
86-2?
76-4?
74-6?
85-8?
84-8?
84-0?
would
indicate
still
more
corresponding
In some
cases
we cannot
expect
of one
was made
large number of observations
are parallel to the cellulose
of striations
exact
set
agreement
of striations.
the directions
between
correspondence
close. Typical
is found to be extremely
from which several further conclusions
more easily visible set of striations
diffraction
giving the more intense
directions
of the
measure
two
were plotted
on paper
the
and, wherever
possible,
the region examined
consisted
of
1931) too small to allow the determination
and in others one of the two sets of
position;
for exact determination
of its direction.
In
indistinct
a sufficiently
that the sets
given
These
method.
position
major extinction
It is true that in some cases there
indistinctness
the
5
alone
demonstration
striations
extinction
too
to the
X-ray
major extinction
position.
of "mosaic"
areas (Preston
spite
4
completely.
in the previous
Small areas, about the size covered by the spectrometer
slit, were
of the cellulose
out on a piece of wall and the directions
chains
paper.
marked
were
X-ray
of the wall, but a series
and under the
spectrometer
to demonstrate
in order
microscope
A method
the
details
out on the X-ray
the correlation
was carried
of observations
of
I
-1 mm. intervals3
12
|
"g
by the slit
in this respect.
is uniform
Table
>3
T. Astbury
W.
chains,
angle between
is a discrepancy
of a few degrees,
time
every
owing to the frequent
this
point in mind, the
Bearing
in the
lies
acute
of cellulose
chains
and
striations
results
are presented
in figs, la, b,
be
In
drawn.
may
every case, the
the
to
set
of
chains
cellulose
corresponds
not only indicate
spots. The striations
they afford also a
importance.
Again, the figure shows
lies in the acute angle
extinction
position
and always closer to the more important
set.
sets
of their
to show
of cellulose
chains,
but
relative
qualitative
that the major
conclusively
the cellulose
between
chains,
is what we should
This, of course,
expect
from
the
multi-ply
structure
Preston
arid
Proc.
Astbury
"*^Vi'hA^'
*\3;h^t^i^?;>c
2%.
7J, vol.
/Soc,
122,
Pfofe
1
^^*^
'./
Fig. 2
Fig. 6
Fig. 5
(Facing p. 80)
Preston
and
Proc.
Astbury
Roy.
Soc,
B,
vol.
122,
Plate
2
**?$*
Fig. 8
Fig. 7
Fig. 9
Fig.
10
The
described
below,
Wall
a structure
with
extinction
of Valonia
which
ventricosa
is in effect
81
a series
of superposed
bireAttention
may be
of observations
on neigh?
not coincident.
fringent
plates
positions
to fig. 16, representing
drawn specially
a set
areas
a
of
piece of the wall. In area A the major extinction
bouring
position
lies about 15? to the left of the more important
set of chains, while in 0,
Fig. 1 a?Directions
wall.
of cellulose
chains and striations
on arbitrary pieces of Valonia
3 mm.
B, on the other hand, represents
away, it lies some 30? to the right.
observed
which
in
an
occurred
in the
only
specimen
abrupt
change
of the striations.
direction
At this point there existed
a definite boundary
the
between
the
two areas, each with its own striations.
From A to the "frontier"
behaved
but
in
this
over
normally;
region they changed
to those in G, and the extinction position
altered simultaneously
in
striations
abruptly
Vol. CXXII?B.
82
R.
D.
Preston
and
W.
T. Astbury
B
A
70?
G
o
D
A-^i-6-^B^-M_^c
D
E
Key diagram
(distances in mm.)
E
of cellulose chains, striations, and major extinction positions
Fig. 16?Directions
at various points on a single piece of Valonia wall (see key diagram). At 23, the
"frontier" region (see text), the two sets of striations and major extinction positions
are drawn separately for clearness; at D and E the limits of variation of the major
Cellulose chains -;
striations-;
extinction position are as indicated.
more important sets-o-o-omajor extinction.;
The
ventricosa
of Valonia
Wall
83
in the direction
of the striations
change
that
the
in
of
cellulose
and there
chains,
change
of the extinction
can be no doubt that the direction
at
position
any point
is determined
by the direction of the chains.
partially
from another
Areas D and E are no less interesting
point of view.
The
a corresponding
manner.
to
a
similar
corresponds
each piece consisted
of mosaic areas much smaller than the area
in the X-ray beam, and the major extinction
varied over
position
area
the
to
a considerable
from
one
mosaic
the
usual two
next, only
angle
Although
included
sets
chains
of cellulose
and
striations
be detected.
could
It is therefore
of the major extinction
is determined
position
not only by the directions
of the cellulose chains, but also by the proportions
One small area in E showed
of the two sets present in the wall thickness.
to the more obvious
a major extinction
set of
exactly
parallel
position
obvious
that
the
direction
with the second set
striations
compared
pronounced
(which was unusually
was structurally
in the area): this particular
different from
area, therefore,
the rest of the wall in that one set of chains was almost entirely
absent.
The majority
of the mosaic
areas,
of two sets of chains
proportions
one
represents
of the
however,
undoubtedly
in the wall thickness,
arise from varying
and this single case
a point raised in the
Perhaps
work
on biological
struc?
Any
alone
must
be
microscope
regarded
of variation.
limits
be emphasized.
paper may again
previous
tures carried out under the polarizing
until confirmatory
evidence
with suspicion
afforded
We
layers
of some
by the X-ray
have, therefore,
and corresponding
80? with
is obviously
each
has been
obtained,
such
as is
method.
of many
consisting
of cellulose
to a network
a wall
other.
visible
microscopically
chains making an angle
of such a structure
understanding
Complete
an investigation
without
impossible
even
decide whether
of that
of the individual
similar to
layer has a structure
layers?to
the wall is composed
of
that of the whole wall, or whether
more or
simply
one
direction
of
each
with
cellulose
less alternating
chains.
only
layers
The work of Correns (1892, quoted from van Iterson
the
1933) supports
the finest
from careful microscopical
Correns concluded
examina?
while the even layers had
the odd layers had one set of striations,
If this is true, then any one layer cannot have everywhere
the other.
the
the
extinction
of
The directions
same thickness.
positions
vary from point
latter
alternative.
tion that
connected
with the relative amounts
to point, a change which is necessarily
of the two sets of chains.
If, then, the same number of layers of each kind
mosaic areas their relative
thickness
are present in two neighbouring
must
vary.
This
work
of Correns
has now
been
verified
by physical
means.
As yet
84
R.
D.
and
T. Astbury
W.
of a single lamella
have been possible.
but even these
can
be
fresh
from
cells,
stripped
Extremely
fail to show any indication
different
of a structure
from that of the whole
It has not yet been found possible
wall.
to strip off a layer with a single
no
direct
tests
thin
set of chains.
the work
of the
Preston
structure
lamellae
On the other
hand,
indirect
evidence
does
certainly
support
of Correns.
As shown by van Iterson,
Jr. (1933), pieces of Valonia wall can be torn
in such a way that the torn edge exhibits
a fringe of fibrils.
Here and there,
the otherwise
straight edge of the wall is interrupted
by sets of these fibrils
a small
van Iterson
gives a drawing
showing
pulled out from the wall,
<->
Major extinction
position
Fig. 3
out from a torn edge and with such a fringe of fibrils.
piece of wall standing
This small piece shows only a single set of striations,
which in the drawing
a single layer in the
are obviously
the origin of the fibrils, and is therefore
this observation
to
sense.
It has been found impossible
present
repeat
to a treatment
similar
Many pieces of wall have been subjected
of van Iterson,
but in no case was it found that the fibrils at the
to the edge.
from the set of striations
edge originated
perpendicular
exactly.
to that
torn
a considerable
On entering
the wall the fibrils obviously
turned through
angle, and finally were lost among the striations
parallel to the torn edge.
It would seem that the fibrils perpen?
Fig. 2, Plate 1, makes this clear.
dicular to the torn edge are the first to break, leaving the two pieces joined
together
by the lateral fibrils which are then pulled out before breaking.
In fig. 3 is given a diagrammatic
of a second
type of
representation
observation
that may be made at a torn edge.
Such an edge often shows
The
of Valonia
Wall
85
ventricosa
a terraced
off of various numbers
effect due to the stripping
of wall layers.
The portion of wall illustrated
is a particularly
of such
interesting
example
a phenomenon.
can
be
seen:
Three distinct
which
the
A,
regions
represents
whole wall thickness;
B, where only a few layers are left; and C, which is
a single layer.
It is unfortunately
to present an actual
impossible
of
this
since
to flatten the wall
photograph
attempts
specimen,
completely
for distinct focusing in the camera caused this part to break up into fibrils.
probably
The striations
marked in the figure, however,
make
positions
it quite clear that the removal
of several wall layers has caused a change
in the orientation
of the major extinction
and that in the region
position,
G the layer consists of a single set of cellulose chains. There can be no doubt
that
the
conclude
each
and extinction
and we may fairly
with one another,
are not identical
layers
from that of the whole wall in that
that their structure
is distinct
is built
chains. The whole wall is composed
from one set of cellulose
its own cellulose chain direction.
of superimposed
each
with
layers
Thus it would seem that, in Valonia,
both striations
and layering
are
in the wall.
related
details
to structural
Now although
the
definitely
from that of the fibres
external
form of the Valonia cell is widely different
of a series
of its wall is essentially
of the higher plant, the structure
The present
below.
be clearly
demonstrated
results,
will
further
accepted
support to the generally
striations
are visible on the walls of cells
cotton
fibres, xylem fibres and tracheids,
the
structure
to
but correspond
closely
true
for the walls
has observed
turn
have
of certain
striations
been
shown
conifer
view
same.
This
therefore,
give
in general,
whenever
of the higher plant (e.g. phloem
hairs) they are not merely artefacts
of the walls. This is undoubtedly
tracheids,
to the major
parallel
to be parallel
that,
the
since
Frey-Wyssling
extinction
position
to cellulose
chains (Preston
(1930)
which in
1934).
and layering
of the plant cell wall
of the striations
significance
discussion
for many years.
has been the centre of considerable
Many cases
have been quoted,
of cell walls with crossed striations
notably
by Reimers
The exact
and Herzog and Jancke
1928). These observations
to phloem fibres (e.g. of hemp, hop, ramie, flax),
one of the sets of striations
showing
usually
pre?
of Nageli that the appearance
of striations
is
conception
(from Steinbrinck
1927,
refer almost exclusively
in which the wall layer
The
dominates.
has been rejected
of high and low water-content
regions
by
and
Krabbe
Schmitz
(1880),
Strasburger
(1898),
(1887),
Dippel
(1879),
are merely distorted
contact
who agreed that in phloem fibres the striations
caused
faces
by
between
"screw
bands"
in intimate
contact.
These
authors
that two sets of striations
can appear in
Nageli's observation
has in turn been
of the wall. Their view of the origin of striations
also contested
one layer
adjacent
86
R.
D.
Preston
and
W.
T. Astbury
he is of the same opinion
impossible;
forward
a
third
in which
hypothesis
(1892), again, put
"
"
the wall is composed
of
Dermatosomes
which aggregate
to form both
and layers.
He considered
to striations,
these "Dermatofibrils, leading
rejected by Correns
as Nageli. Wiesner
(1893) as physically
a
or its derivative",
to be separated
by layers of "some protein
of the original protoplast
of the cell; but repeated
experiments
by
Correns have failed to show any trace of protein in the wall. The primary
a protein complex
and
cell walls of plants certainly
contain
(Tupper-Carey
somes"
residue
for any considerable
1923), but there seems to be no evidence
of protein in the secondary
layers such as are under consideration
Priestley
amount
here.
There
can be little
doubt
that
the
effect
of difference
in water
content
is only of secondary
of layers and striations
visibility
importance
in chemical
is inseparably
connected
with a difference
constitution.
and others (van Iterson
Hess, Ludtke,
1933) have been led, on the basis
the
of partitions
of non-cellulosic
to
of swelling
assumption
experiments,
on the
and
this
conception
their
argument
Eckerson
and
which
bodies
pectin,
layers and even the fibrils, and the fact that
fails to account
for certain phenomena
does not invalidate
It
is
in
this
to note that Farr
interesting
respect
outright.
between
substances
the wall
(1934) have
they describe
observed
in the protoplasm
minute
recently
as cellulose
surrounded
a
particles
by
layer of
is perhaps
of this observation
significance
open to
the
although
question
1935). At the same time, the view that striations
of fibrils by less perfectly
are due merely to the separation
oriented
regions
cannot be entirely
of the same composition
disregarded.
and Kerr
(Bailey
The
of the
None
difference
Organization
observations
between
the
of the
Wall
as a Whole
above
presented
suggests
any fundamental
wall of Valonia
and that of the fibres of the
cell
in cell size, and the correspondence
higher plant, in spite of the difference
is again evident
when we come to consider
the details of the organization
of the wall as a whole.
The modification
whose
walls
of wall
are wound
with
which must occur at the tips of cells
structure,
a molecular
been a point
spiral, has hitherto
of mere
cannot
fore,
and any investigation
conjecture
throwing
light on this subject
fail to be of considerable
value. The opportunity
was taken, there?
of carrying
out a survey
of the whole
Valonia
wall. The uncertain
visibility
of the wall striations
made
it impossible
to follow
microscopically
The
their
Wall
of Valonia
87
ventricosa
directions
had
round the cell, so the investigation
uninterruptedly
out by X-rays.
A herbarium
of V. ventricosa collected
at St Croix and sent to
specimen
to be carried
us by Borgesen,
to whom our thanks are due, was emptied
of its contents
a small perforation.
a fine glass capillary
Into this perforation
through
tube was inserted and fastened
in place by a minute ring of cellulose cement,
whence by alternate
and
emptying
filling of the cell with distilled water the
remains
of the protoplast,
Incrustations
etc., were finally ejected.
clinging
to the outside
of the wall were removed
with
treatment
by subsequent
on the
rigid to be mounted
N/20 HC1. When dry, the cell was sufficiently
the capillary
tube to a brass arm with
by clamping
careful
adjustment
By
any part of the wall could thus
be set perpendicular
to the X-ray beam.
In order to obtain reference
lines
the directions
of the cellulose
as given
chains
whereby
by the X-ray
X-ray spectrometer
a universal
joint.
could be transferred
to the cell itself, the following
procedure
photograph
was adopted.
The cell was mounted
on a spindle
by means of which it
and a series of
could be rotated
and raised through
measured
distances,
circles round the cell, was
lines, some 3 mm. apart and forming
complete
of
ink using a modification
of the usual inking
traced in Indian
system
to the spectro?
etc. A pair of straight wires was then attached
barographs,
meter so that they could be set parallel to that part of a line on the cell
and would cast a shadow
on the
to the area under examination,
nearest
film. In general,
this area under examination
was arranged
the spectrometer
film was placed
slit, while the photographic
It was then quite a simple
as near to the other side of the cell as possible.
between
the diffraction
matter to differentiate
spots produced
by the two
photographic
just to touch
sides of the cell (see fig. 4).
opposite
was used similar
In order to obtain a map of the whole wall a method
of mapping
"lines of force" method
fields. The
to the familiar
magnetic
determined
at
in
the
were
an
wall
and were
chain directions
point
arbitrary
had shown that the
experience
constant
over a length of 1| mm.
A second point was therefore
chosen,
1| mm. from the first in the direction
and the directions
This
of one of the sets of chains,
again determined.
round the cell using only one set of cellulose
chains.
process was continued
then
drawn
direction
upon
of either
In general
directions
certainty
intermediate
the wall.
Now
set of chains
previous
was almost
no difficulty
was experienced
at a new point corresponded
where it arose being entirely
A starting
in determining
which of the two
to the one being traced,
any un?
the
of
removed
by
investigation
points.
point
was
chosen
about
midway
between
the
base
and
tip
88
R.
D.
Preston
and
W.
T. Astbury
of the cell, where one set of chains was found to lie approximately
along a
and
the
this
the
base.
On
the
chains
direction,
joining
tip
following
the hold?
were found to form a great circle round the cell, passing amongst
the value of this set of
fast scars and across the cell apex.
Unfortunately,
line
was somewhat
of the
reduced by very considerable
dispersion
near the holdfast
X-ray diffraction
spots in certain
particularly
regions,
scars and the cell apex.
of the second set of chains, however,
Investigation
this result in a very striking
confirmed
At each point on this
manner.
observations
Fig. 4?Illustrating
the method of transferring cellulose chain
photographic film to the cell itself. A, spectrometer slit; B,
parallel wires; D, and E, diffraction spots produced by the part
and further from the slit, respectively; F9 shadows cast by the
second
track
both
directions
of cellulose
chains
were
directions from the
Valonia cell; C, two
of the wall nearer to
wires C.
marked
in ink upon
chain direction
the wall, although
The second
only one of them was followed.
was thus found to make a slow spiral round the cell, the turns of the spiral
smaller as the apex and base of the cell were approached
until
becoming
finally,
both
photograph
were strictly
and the base, a point was reached where the X-ray
of Valonia was no longer obtained.
Both points
and gave a photograph
of a series of rings
consisting
at the apex
characteristic
localized
a crystalline
It is important
to note that
powder.
be
were
discovered
not
termed,
may
by accident
such
as is obtained
from
these
two "poles",
as they
The
Wall
89
ventricosa
of Valonia
or by a method
of trial and error, but by painstakingly
the spiral
following
of chains round the wall. They would appear to be produced
by the
wall deposition
mechanism
of the plant rather than by any local, accidental
set
change
Valonia
in
environmental
wall
conditions.
A model
of the
structure
of the
in fig. 5, Plate 1, in which one "pole"
can be seen
towards the upper end. The X-ray photograph
of this "pole" is reproduced
in fig. 6, Plate
1. It may be pointed
out that the second set of chains
recorded
at each point of the spiral may be linked up with chains imme?
is shown
above and below and that the circles thus obtained
form, so to
the
two
it
is
an
invariable
Whether
speak, "meridians"
uniting
"poles".
rule that one set of chains always forms great circles uniting
the tip and
base of the cell, as in the present case, is not yet clear. A decision
on this
diately
cell; and only one of
point is best made upon a long, narrow,
cylindrical
this type was available.
In this one specimen,
one set of chains
however,
was observed
a
"meridian"
to run approximately
at
all points of the
along
wall which were investigated.
We may thus picture the Valonia cell wall
as consisting
in great
of two crossed sets of cellulose
chains, one running
circles (possibly
always from base to tip and back), and the other forming
a slow spiral round the cell axis joining the two points of intersection
of
these great circles.
It has been
out above that at the base of the cell, near one of
pointed
in the otherwise
there occurs some disturbance
"poles",
regular ap?
In
this
of
the
wall
surface.
clusters
of
rim-like
raised,
pearance
region,
the
structures
be observed
(holdfasts).
can still be seen
rhizoids
and
may
In
rhizoids
some
which
few
attached
mark the sites of previous
obviously
in
the
cases
available
the
specimens
to the cell in the form of long, narrow,
into trumpet-shaped
attachments
at the
widening
be
in
a
rhizoid
seen
the
Such
point
may
photomicrograph
of the surface of the basal region of a cell shown in fig. 7, Plate 2. The
in methylene
blue to bring
shown in this figure was stained
preparation
hollow
cylinders
of connexion.
that the wall
out the fact, which is perhaps more obvious in cross-section,
This no doubt explains
thinner inside the rims than outside.
the
If
a
obtained
in
these
rhizoids.
we
choose
rim
of
such
X-ray photograph
is much
in the X-ray
as just to be included
beam, then the X-ray
appears to arise solely from the rim. Although
pattern obtained
in structure
the wall inside the rim seems to be identical
with that outside,
a diameter
diffraction
and the striations
its thickness
on it are continuous
is so small
with
with
that
those
on the rest of the wall,
that its X-ray
of the rim itself
compared
does not mask that of the rim. The X-ray
photograph
of such a rim was found to consist of a series of concentric
microphotograph
rings,
indicating
90
R.
random
should
arrangement
from
expect
D.
Preston
of the
and
W.
T.
Astbury
what we
This is exactly
particles.
of cross-sections
of the wall.
Fig. 8,
of such a cross-section.
Here the remains
cellulose
consideration
Plate
2, is a photomicrograph
of a rhizoid are seen clinging
imme?
to the wall (on the left) and located
above a small cell cut off from the parent. The whole structure
is
diately
filled with small granules
which appear to be plastids
surrounded
by a
thick
layer of starch, and may perhaps
play a part
of the rhizoid.
It is clear from the photograph
that the
development
rim seen in surface view consists merely of a ring of the outer layers
wall turned on edge, and the X-ray photograph
is in effect that of a
comparatively
section
The
and
of a cylindrical
holdfast.
structure
of the rhizoids
by the
X-ray
as illustrated
microphotograph,
by other workers
raised
of the
cross-
8, Plate 2,
with the
agreement
in figs.
is in complete
in the
7 and
descriptions
given
i860;
(Famintzin
1905).
Borgesen
It is quite clear that the cylindrical
as small cells cut
outgrowths
originate
off on the inside of the "main"
vesicle by surrounding
a small collection
of the necessary
masses
curved
plasma
wall,
by a strongly
subsidiary
before the deposition
of the wall of the mother cell is complete.
As more
and more layers are deposited
over this "watch-glass"
wall, by the con?
tinuous
of new wall substance
deposition
by the
buried in the wall. It may well be that
eventually
of this small cell is then considerably
thinner than
At the same time it must be noted that the inner
interior
open sea, but on a virtually
incompressible
parent cell, it becomes
the wall on the outside
that
on the inner
wall borders,
side.
not on the
supported
by compara?
It is not surprising
that if the "watch-glass"
tively firm walls.
therefore,
cell begins to expand the expansion
takes place towards
the outside.
This
would explain the formation
of both rhizoids and bud cells on the outside
of the parent plant.
we meet with a difficulty.
Here, however,
Whereas
the bud cells are usually
almost
in form, rhizoids
are always
spherical
as long, narrow
Hitherto
no explanation
of this
produced
cylinders.
of essentially
similar cells has been possible.
Now that
of the plant has been determined,
we find that the
rhizoids
arise from regions of the wall adjacent
to the poles of the spiral,
and it is not unreasonable
to suppose
that the difference
in behaviour
of
"
cells is connected
with the difference in wall structure.
watch-glass"
Such
a connexion
could, of course, be traced only in the vaguest terms at present,
and its investigation
is a subject for further research.
divergent
the wall
behaviour
structure
The
It has been mentioned
(1931)
surface
in Valonia
is only partly
clear that any
ventricosa
of Valonia
of Cellulose
Relation
that
Wall
Chains
to Wall
91
Surface
arrived at by Sponsler
already that the conclusion
the planes of 6-1 A. spacing lie parallel to the wall
it
In the course of the present
research
justified.
built up by
results
obtained
from blocks
X-ray
It was
many pieces of the wall are liable to be misleading.
superposing
the
to
of
the
advisable,
therefore,
reinvestigate
question
angular
thought
of the cellulose
chains, using single pieces only. To this end a
dispersion
became
small
area of wall was selected
and whose
X-ray photograph
over the other.
Fig. 9, Plate
its
of studying
regarded.
The most
showed
one set of striations
predominated
of one set of chains
a preponderance
of the area chosen:
2, is an X-ray phonograph
is so much more intense
than the other that for the
one set of reflexions
purpose
on which
dispersion
angular
the
weaker
set
may
be dis?
of the
the angular dispersion
of demonstrating
Plate
the
shown
in
2,
10,
by
photograph
fig.
for which the flat piece of wall was mounted
on
the
spectro?
horizontally
meter with the main set of chains parallel to the X-ray beam.
If now, as
cellulose
direct
chains
method
is illustrated
the cellulose
chains had been lying in only one orienta?
Sponsler suggested,
tion round their axis, not arcs, but spots as definite as those in fig. 9, would
The photograph
have appeared
in the photograph.
reveals in fact quite a
both
the
inner
sets
for
of
of
arcs (corresponding
to
considerable
dispersion,
6-1 and 54A)
can be traced round a complete
circle.
planes of spacing
at fairly definite
does decrease
The intensity,
however,
certainly
rapidly
it may be said that the normal to the plane
limits, and roughly
speaking
6-1 A is confined
of spacing
the wall surface.
to about
60? on either
side
of the normal
to
Discussion
of the wall of such a large cell as
remarkably
regular organization
result of this research.
The
of Valonia is perhaps the most interesting
similar
to
that
of
the
that the cell has a structure
fundamentally
The
that
fact
the essential
fibres of the higher plant serves once more to emphasize
It has long been a question whether
phenomena.
biological
underlying
here, could be regarded
cells, such as we have under examination
coenocytic
of higher plants containing
with the protoplasts
as single units comparable
but as regards the wall at least there can no longer be
but a single nucleus,
minute
unity
any
doubt
about
this.
The
wall
of
Valonia
would
appear
to be just
as
92
D.
R.
uniform
as that
in structure
of a single
and
Preston
as that
W.
of uninucleate
T. Astbury
cells
and can be regarded
only
cell.
The appearance
in wall structure.
is of course not a novel phenomenon
striations
that in bast fibres the secondary
It is widely recognized
wall is laid down in definite layers and that these layers can be striated in
different
fibres from hemp and hop plants have
directions.
For example,
two secondary
round the cell in a
the
striations
on both running
layers,
of crossed
right-hand
spiral, with the spiral on the outer layer less steep than that
show
on the inner.
On the other hand, bast fibres from flax and oleander
the spirals on the two layers being of opposite
crossed striations,
definitely
of cell the view put forward by Nageli that
As
in a single wall-layer
is no longer held.
in
different
directions
has been shown above in the case of Valonia, striations
the similarity
occur in different
wall layers.
Here, however,
invariably
ceases. Whereas in bast fibres change
between
Valonia and fibres effectively
in both types
sign. Moreover,
crossed striations
can appear
of one layer
in spiral sign occurs but two or three times and the structure
is not repeated
has
numerous
a
in
layers which
subsequent
layer, Valonia
This
manner.
in a very exact
alternate
in striation
direction
regularly
of alternate
deposition
chains
as
layers,
layer but
each
with
the
same
direction
of molecular
intricate
one, presents
perhaps
im?
in
It
seems
as
encountered
botany.
problem
yet
to invoke
the idea
of pseudowithout
modification
serious
possible
of new substance
on an old wall such as is often put forward
crystallization
the
last
in wall
in discussions
the
the
formation
of wall
mechanism
deposition:
involves
down.
arise
as a result
at the least, it must
halt in the
a periodic
growth
old wall in orienting
new layers.
The existence
of "mosaic"
areas
laid
most
be recognized
effectiveness
that
of an
on the lines already
point to point in the
It
in the wall thickness.
is to be explained
from
of variations
They
chains
of the two sets of cellulose
proportions
are due rather to a varying
to suppose that these variations
seems reasonable
The
in their number.
thickness
of the wall layers than to a fluctuation
the formation
underlying
of the wall during
in fracture
mechanism
of mosaic
areas
is no doubt
as already
development,
sought
by one of the present writers (Preston
1931).*
form of the path followed
With regard to the geometrical
chains it would appear that this approximates
set of cellulose
to be
suggested
by the
most
spiral
to an
* This idea is
supported by the fact that remnants of wall layers, presumably the
original outer layers, are often found clinging to the plant when collected. This has
been pointed out to us by Dr Steward, of Birkbeck College, London, who recently
had the opportunity of studying Valonia in its native habitat.
The
ventricosa
of Valonia
Wall
93
on the surface of a spheroid.
equiangular
Pig. 11 illustrates
spiral described
a prolate spheroid,
fair description
of many Valonia
which is a reasonably
cells. If the spiral at any point (0, <fi) of its path makes a constant
angle oc
=
that point, then
with the meridian
constant)
(6
through
cot a = Ss jySd
6 cot a =
or
Fig.
the solution
of which,
# cot a =-^?
For the sphere
26
this
if 6 = 0 when
cos -l
?
ds/y,
11
=
7r/2, is:
-cos
icosh-1
20]-i
reduces
*262
cot2 ^H-ll.81
to:
6 cot a = log tan 0/2,
as may
be readily
derived
directly.
* This general formula is given here in case experimental
later of testing it rigidly.
opportunity
should arise
94
R.
D.
and
Preston
T. Astbury
W.
It should be noticed that dcfr/dd = 0, when 0 = 0 and n, and is a maximum
when 0 = 7r/2, as was actually
observed
for the Valonia cell described
above.
a practical
it is hardly
proposition,
test
of
the
quantitative
equation,
though it may
examination
of more abundant
than was available
material
to irregularities
to make a strict
Owing
however,
be that careful
of growth
for these
would reveal specimens
At the
experiments
sufficiently
perfect.
we are justified in saying only that the angle a is roughly constant
and not far removed
from a right angle?the
mean of the values given in
Table I, for instance,
is about
83??and
that the spiral reproduces
the
moment
features
of the path of a point moving
on the surface of a spheroid
a constant
with
the
meridians.
angle
of angle between
The approximate
meridians
and spiral that
constancy
is maintained
alternate
and
the
fact of alternating
through
layers,
deposi?
main
so as to make
tion
best
seems
itself,
mechanism
orienting
Recent observations
explained
embodied
for the time
in
on the cytoplasm
are strongly
for instance,
extract
from Chadefaud's
suggestive
being
in terms
of a rhythmic
the
polynuclear
protoplasmic
lining.
of algae, those of Chadefaud
(1933)
of such a mechanism,
and the following
"
d'une structure
Existence
infra-visible
paper,
chez les Algues",
du cytoplasme
is very much to the point:
orientee
du cytoplasme
d'une structure
orientee
se traduit
d'une
"L'existence
dans les grandes cellules allongees
du tissue
facon encore plus interessante
Le cytoplasme
de Chorda filum.
de ces cellules possede deux series
a peu pres orthogonales,
et fortement
inclinees
de lignes directrices,
par
l'axe
L'une
de
a
de
la
cellule.
ces
directions
est
longitudinal
rapport
central
elle
preponderante:
chondriosomes
en
fuseau.
direction.
oriente
la plus grande
des pheoplastes,
des
partie
de physodes,
et tous les noyaux,
sont
etires
qui
seulement
sont orientes
selon l'autre
pheoplastes
et des amas
Quelques
Or, il est tres
curieux
la structure
de remarquer
que ces deux
avec celles des deux
directions
coincident
de
de
cytoplasmique
systemes
la membrane
et que revelent
que presente
celluloso-pectique,
en X de cette membrane.
de facon tres nette les ponctuations
On trouve
ainsi une relation
evidente
et celle de la
entre la structure
cytoplasmique
fines
stries
membrane
cellulaire."
The occasional
appearance
sets of cellulose
predominating
to set up a spiral
the
structure
fairly
van
between
of opposite
fibres,
of the
of a third
the two
lying between
of attempts
chains is possibly a manifestation
still another link with
sign and may represent
in which
orientation
the
occurrence
of spiral
reversals
common.
Iterson
(1936)
the cellulose
considers
crystallites
that
the
approximate
in adjacent
layers
relation
orthogonal
of
of the wall
Valonia
is
The
Wall
of Valonia
ventricosa
95
a consequence
of an alternation
of wall stretching
and protoplasmic
of easiest stretch being at right angles to the length
the direction
streaming,
laid down. The periodic
of the crystallites
would be
already
stretching
each day in the turgor pressure in the cell,
caused by the strong increase
and it is supposed
that the stresses
for example,
so set up determine
the
is simply
direction
the next layer with the
as it deposits
protoplasm
this
direction
of
The
flow.
lying along
concept
perhaps marks
in the sense that it offers something
rather more concrete
to
of flow
crystallites
an advance
of the
of the process and does not
on, but it still leaves vague the initiation
can take place in a multi-ply
how stretching
structure
first in one
explain
at right angles. The idea may be valid for
direction
and then in a direction
a wall consisting
of two layers only, but it is not easy to see how the
work
mechanism
continues
In any case,
stage.
is that the average
to be sure
though
secondary
to operate with such angular regularity
this
beyond
the impression
gained from the studies reported above
is definitely
less than a right angle,
angle of crossing
it might
be possible
to trace
this
deviation
to some
source.
to the question
of the approximate
orienta?
6-1 A, a recent paper
cell wall of the planes of spacing
From an X-ray study of the various
by Sisson (1936) is very illuminating.
that
can
be brought
about artificially
orientation
of
in
crystallite
types
that
in
cellulose
Sisson
concludes
bacterial
of
membranes
general whenever
reverting
Finally,
tion parallel to the
once more
whether
in one direction,
a sample is constricted
by drying or by pressure,
an
inherent
to set themselves
have
then the cellulose
tendency
crystallites
6-1 A normal to the direction
of constriction.
of spacing
with the planes
that to explain in Valonia?or
appear, therefore,
observed
selective
orientation
for that matter?the
It would
wall
about
more
their
long
complicated
it is probably
unnecessary
the simple act of drying.
directions
than
in any cellulose
of the crystallites
to invoke
anything
to Professor J. H. Priestley
wish to express their indebtedness
with Miss L.I. Scott, for valuable
in the work and, together
side. Their thanks are due also to Dr F. C. Steward
on the botanical
The authors
for his interest
help
for a supply of lamellae
and
stripped from fresh cells of Valonia ventricosa,
the equation
of an equiangular
to Mr H. J. Woods for extending
spiral
on a sphere to the more general case of a prolate spheroid.
described
For
are
indebted
to
the
of the research
the expenses
of
the
they
generosity
of Clothworkers
Company
Worshipful
of 1851.
the Exhibition
and to the Royal
Commissioners
of
96
R.
D.
Preston
and
W.
T. Astbury
Summary
The cell wall of Valonia
ventricosa
has been
studied
in detail
and the polarizing
X-ray diffraction
photographs
microscope.
It is found to consist of layers in which the cellulose
chains
layer
are inclined
to those
in the
and
preceding
subsequent
angle which is on the average rather less than a right angle.
of meridians
The chains of one set of layers form a system
while those of the other set build a system
of spirals closing
by means
of
in any one
layers at an
to the wall,
on the
down
defined by the meridians.
"poles"
on the layers of the wall correspond
The two sets of striations
closely
of cellulose chains, while the extinction
to the meridian and spiral directions
and by the relative
directions,
being defined both by the directions
pro?
two
between.
portions of the two sets of cellulose chains, lie in variable positions
The development
of the rhizoids has been investigated
and found to be
to the poles of the spiral.
with regions of the wall adjacent
associated
6-1 A of the cellulose
The plane
of spacing
is, roughly
crystallites
confined
within an angle of about 60? to the wall surface.
speaking,
It is suggested
that the path of the cellulose spiral is that of a logarithmic
on the surface of a sphere or prolate spheroid.
(equiangular)
spiral described
The
higher
relation
plants
is traced
and that
between
the
of the cell wall
structure
of the
walls
of fibres
of
of Valonia.
References
Astbury, W. T., Marwick, T. C. and Bernal, J. D. 1932 Proc. Roy. Soc. B, 109, 443.
Bailey, I. W. and Kerr, T. 1935 J. Arnold Arb. 16, 273.
Borgesen, F. 1905 Overs, danske VidensJc. Selsk. Fork. p. 259.
Chadefaud, M. 1933 CM. Acad. Sci., Paris, 196, 423.
Correns, C. E. 1892 Jb. wiss. Bot. 23, 254.
? 1893 Ber. dtsch. bot. Ges. 11, 410.
Dippel, L. 1879 Abh. senckenb. naturf. Ges. 2, 154.
Famintzin, A. i860 Bot. Ztg, 18, 341.
Farr, W. K. and Eckerson, S. H. 1934 Gontr. Boyce Thompson Inst. 6, 309.
A. 1930 Z. wiss. Mikr. 47, 42.
Frey-Wyssling,
and Reproduction
of the Algae",
1.
F. E. 1935 "The Structure
Fritsch,
Cambridge.
Hengstenberg, J. and Mark, H. 1928 Z. Krystallogr. 69, 271.
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? 1934 Philos. Trans. B, 224, 131.
Schmitz
1880 S.B. niederrhein. Ges. Nat.- u. Heilk. 37, 200,
The
Wall
of Valonia
ventricosa
97
Sisson, W. A. 1936 J. Phys. Ghem. 40, 343.
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15, 978.
Steinbrinck, C. 1927 Naturwissenschaften,
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-1923
van Iterson, Jr., G. 1933 Ghem. Weekbl. 30 (1), 2.
? 1936 Nature, Bond., 138, 364.
usw." Wien.
Weisner, J. 1892 "Die Elementarstruktur
Description
of Plates
Plate 1
Fig.
2?A typical fringe of fibrils at a torn edge of Valonia wall. Note that on
entering the wall the fibrils turn round and finally disappear among the
striations almost parallel to the edge.
Fig. 5?Model of the wall structure of V. ventricosa showing the spiral organization
of one set of cellulose chains. The spiral can be seen closing in towards the
point marked on the model, which thus represents one "pole".
Fig. 6?X-ray
photograph of the wall of V. ventricosa at a "pole" of the spiral.
Plate 2
of the basal region of the wall of a cell of V. ventricosa.
Fig. 7?Photomicrograph
of the point of attachment of a rhizoid, in cross-section.
Fig. 8?Photomicrograph
cell from which originated the
On the right can be seen the "watch-glass"
rhizoid whose remains are attached to the wall on the left.
Fig. 9?X-ray
photograph of an area of the wall of V. ventricosa in which one set
of cellulose chains greatly predominates.
(X-ray beam perpendicular to the
surface.)
Fig. 10?X-ray
photograph of the same specimen lying horizontally with the main
set of cellulose chains parallel to the X-ray beam.
Vol. CXXII?B.