Neerl.
Acta 801.
29
(1), February
1980, p.
Development
of
Linum
ovule
and
usitatissimum
testa
L.
Boesewinkel
F.D.
de
Hugo
Vries-laboratorium,
DD
1018
of
17-32.
Universiteit
van
Middenlaan
Amsterdam, Plantage
2A,
Amsterdam
SUMMARY
The ovule
are
inner
the
primordium
of Linum usitatissimum is trizonate
of dermal derivation.
is
layer
The inner
developed as
an
and both the outer and inner
integument ultimately
endothelium,
and the middle
becomes
about
14 cell
integument
layers thick,
about the ultimate
layers bring
the
shape
of
seed.
ripe
The seed-coat
is formed out of the outer
integument
and the outer and inner
of the inner
layers
integument.
The outer
this
layer
of the seed-coat consists of slime
layer through
ruptures in the cuticle and forms
the seed-coat consist of the fibrous cells of the
latter contain
pigment
Geraniaceae,
Oxalidaceae
1.
and have
or
pitted
walls.
cells. In
a
exotegmen
The
an
medium slime diffuses from
aqueous
coat around the seed.
and
of the cells
of the Linaceae
family
The mechanical
of the
layers
of
endotegmen, which
is assumed to be related to
Malpighiaceae.
INTRODUCTION
The
family
mostly
of the
woody
Davis
(1926),
Linaceae is
representatives
or
The genus Linum is
most
of the
other
multicellular
cells
parietal
veloping
sporal
cells have
omic
journals
Meyer
genera. The ovules
and
gives
are
to
Netolitzky
are
anatropous,
and
a
variable
somewhat chaotic
retarded
of linseed
form the
to
most
of Linum usitatissimum
and manuals (see, e.g
.,
of the
are
sac.
because
numerous
On
massive,
a
primary
Gevaudan the
compressed. Only
embryo
found in
have
presence of
to
impression
and become
growth
the
regards
as
1966). According
than
specialised
more
cultivated flax
account
publications
most
one
and
pharmacological
of these
of the
on
de-
arche-
econ-
the
seed
agricultural
Flückighr 1867, Tschirch & Oesterle 1900,
1901. Moeller & Griebel
1928, Wiesner 1928, Gassner
1931, Hay-
1938).
ward
Both
in
integuments partake
conspicuous
as
layer
is the
Schleiden
outer
1857)
the
the
layer
surface of the cell wall of the
boiling
or
by shaking
water.
seed-coat but the
According
cells contain
slime-forming
epidermal
in cold
of the slime from the
formation of the
of slime cells.
epidermal
but Kutzing 1851 believed that the
origin
1931). According
the linaceous ovules
of the
Davis
1959;
development
importance
anatomy
(such
a
its distribution and contains
predominantly suffruticose
archespore
cells attains full
(1976)
in
tenuinucellate.
(Gevaudan
nucellus
(Winkler
and Corner
(1966)
and crassi-
bitegmic
chiefly tropical
a
(1855)
most
older workers
mucilaginous substance,
matter
cells and becomes
Cramer
to
was
secondary thickening layers
is found
on
suspended
the first
of the
to
in
the
outer
water
by
describe the
outer
epidermal
18
F. D.
cell wall, which observation
confirmed
was
by
Frank
Haberlandt(1918) the slime functions principally
a
different explanation
seed
to
the soil in
composition
of the linseed
Löwe
(1947),
layers
of the seed
ultimately
Erskine &
2.
so
of
out
more
mucilage
given by
were
outer
MATERIALS
AND
pigment
L.
and
L.
Desf.
grandiflorum
(Hortus Botanicus)
of the
University
and Allen-Bouinmixtures. Sections
Mature seed-coats
techniques.
The
following
The mechanical
(1958).
of the innerintegument, which
oriented fibrous
which is
integument
ultimately
cells.
METHODS
The material of Linum usitatissimum L.,
flavum
layer
producing
Details of the
1974).
axis) longitudinally
of this
layer
less thick-walled
the attachment of the
Mangin (1893), Anderson &
Jones (1957), Hirst & Jones
formed out of the
to
reservoir, but later
the chance of
regions
1919 and Grubert
(Murbeck
of the innermost
or
function, viz.,
that in arid
consists of (in relation to the seed
elements, and
up
are
of its main
given
place
becomes greater
offspring
built
was
moist
a
(1866/67). According
a water
as
BOESEWINKEL
specific
L.
L.,
collected in
narbonense L.,
the
made by
means
embedded both in
used:
were
L.
Botanical Garden
of Amsterdam. Fixation took
were
were
strains
L. perenne
was
in Craf
place
of standard microtome
paraffin
phloroglucinol
wax
and in epon.
HC1,
-
Sudan
IV,
ruthenium red and IKI.
The SEM studies
a
carried
were
gold-palladium sputtering
consisted of
a
shorter
longer
or
out
with
were
stripped
cut
off
or
through
or
hand sections of treated and
of
light microscopy
layer,
3.
so
expose the
was
or
Stereoscan Mark 2a after
treatment
in
10%
of intact seeds
HNG
3
.
of the seed and seed-coat intact
applied;
underlying
subsequently
in absolute ethanol
certain
structure.
air-dried seeds
were
(to prevent swelling
layers
could be
In addition, free
studied by
of the
means
mucilaginous
that the structural features of the cell walls could be better
observed).
RESULTS
Linum usitatissimum has
adjacent
3.1.
ovules which
Ovule
The ovule
a
are
pentamerous pistil with in each ovary chamber
sometimes abortive. The fruit is
a
surrounded
The
from small
by
primordia
the
are
protuberances
on
trizonate and consist of
initially only anticlinally
a
either side of the
corpus
dividing layers
matogen (1 2 ) and dermatogen (1,). The subdermal archespore
and its cells
ovules
layer,
are
parietal
small and is
two
capsule.
ontogenesis
promordia develop
gynoecial septa.
A)
to
water
structure
fragmentation
rubbed away
Cambridge
immersion in
For the observation of the internal
seeds
a
for 3 min. The
treatment
fairly large
cells
can
completely
and the
epidermis
and
somewhat rich
be discerned
built
up
whose
by
(Jig.
the
apical
I A,
in
C).
cytoplasm.
already
3
is
In
in fig.
pluricellular
some
the cells of the
start
I
subder-
of the
The nucellus remains
archespore,
cells
(1
of the
fairly
subdermal
dividing periclinally
at
OVULE
and
oi
corpus,
=
=
an
TESTA
1.l.s. of
Fig.
es
AND
developing ovules
of Linum usitatissimum.
sac;
en
=
endothelium;
integument;pvs
=
end
can
shown in
still be
(figs.
be
distinguished
fig.
(Gévaudan
tropous curving
complete ring
1
Finally,
I
vestiges
the
B)
becomes
2
1
and
3
:
and
(fig.
by periclinal
primarily
starts
I
A).
and
more
e.s.
(es)
dermal
before
a
nucellus;
layer,
subdermal
cot
=
ii
layer
=
inner
is
integument;
cotyledon.
advanced stages
corresponding
no
parietal
with
those
sporogenous tissue
formed in
is formed
The inner
as
=
degenerated
sac
oblique
growing
3-layered by periclinal
nuc
obturator;
the stages
of the
embryo
=
In
At
1959). Already
commences
wall
ob
A-E).
1 E, 2). The tetrade is linear and the
chalazal end
fig.
1
1,
endosperm;
longer.
any
I D and E the
recognised.
=
provascular strand;
early stage of development (fig.
cells
1
respectively.
embryo
outer
19
OF LINUM
by
the megaspore
integument
2-layered
divisions in its inner
or
initiation the
structure
1
but
D).
fairly
the
ana-
3 dermal cells
layer (fig.
top
at
integument (ii) originates
divisions in 2
can
the nucellus
as
a
(see
soon
Soon after
20
BOESEWINKEL
F. D.
the
of these
beginning
layer
ultimately
becomes
stretching
of the
divisions of the middle cell
periclinal divisions, periclinal
the
repeatedly throughout
occur
very
thick
i.i.
developing
E
I
(Jigs. 3A, 2). Fig.
cells of the innermost
cytoplasm-rich
I
(fig.
E)
that the
so
shows
already
layer
1.1.
the radial
of the i.i.
which
later form the endothelium.
The
Due
a
to
the arrested
en
grows
development
dermal cap,
than
so
that the
stages remains
velopmental
more
cells thick
two
divisions in the inner cell
3.2.
the
The
fully developed
of the
full-grown
has
of the
originally
the
most.
In the
The o.i.
a
in later de-
and
becomes
locally
place by periclinal
of the ovule.
and crassinucellate
bitegmic
longitudinally elongate;
at
According
this stage the
Davis
to
micropyle,
(Jig.
enlarged
the
(1966)
2).
e
s
is
e.s.
is formed
formation
Davis
(1966)
of
seed
initially
The lower part of the
functions
as
severed it
ceases
The
shape
radially
e.s.
(Jigs.
to
by
as
the
connects
dermal cells
(Jig. iD). According
to
so
becomes
The
at
stylar
developed
in the
complete.
e.s.
Cell
According
to
separated
from the remainder as
integument (Billings 1901, Schur-
detached part
but
epidermis
becomes
and the
after
it
of the
has
and
of the i.i.
e.s.
become
originally
completely
gradually changes
ultimately they
tightly joined
resorption
Van Wisselingh
endosperm
place
peripherically
becomes
flattened and
layer
endosperm
divisions take
thick
channel somewhat
such.
tangentially
This cell
and
the inner
1919).
wall formationin the
cuticle between
which
remnant of
and L. narbonense resemble those of L.
haustorium
function
to
D).
narrow
a
layers
seed-coat
and
of the cells of the inner
3C.
a
cytoplasm-rich
flavum
gradually
endosperm
stretched
as
12 cell
a
only partly
is of the helobial type.
Wisselingh
an
i.i.
nuclear and is situated
endosperm
Van
the
is about
The obturator,
proceeds centripetally
the
The i.i.
is covered with
the result of a local constriction
1924,
by
plane.
which cell represents
(Jig. 2)
resembling
an
closely.
Development
is
structure
part of the nucellus sometimes
trichomes. The ovules ofLinum
endosperm
endothelium a
cytoplasm-rich
basal
the funicular
usitatissimum very
rous
initially incomplete
edge
nucellar apex.
micropyle
in
canal and the
hoff
only
ovule
pluricellular archespore.
The
compressed
wall
1 B-E).
(fig.
be discerned in the form of
asymmetrical.
either
on
the division
side later
raphal
after fertilisation has taken
is found
sporogenous cell
developed
the
3.3.
o.i. cells at the
can
by
structure
Polygonum type.
cuticle is present.
The
is
ovule is anatropous,
At the inner side of the
as
wall
two-layered
a
young
markedly
layer
resorbed the
already
ring
only
The nucellus is slender and
a
into
out
vague indication of the presence of the o.i.
small
after the i.i., also
integument (o.i.) originates shortly
outer
of about three dermal cells
(1919)
to
places
the
endosperm
and Netolitzky
attain
after
of the middle layers of the i.i.
seed-coat. In the middle
that it may in
from
become tanninife-
a
layers
(1926)
there is
of the i.i.
thickness of up
to
some
14 cell
OVULE
Fig.
2.
AND TESTA
OF
21
LINUM
Fully developed
ovule of Linum
usitatissimum.
22
Fig,
F.
3. Ovule
(A)
and
development
of seed-coat
as seen
in
cross
sections.
D. BOESEWINKEL
AND
OVULE
that stage forms the bulk of the volume of the
at
and
layers
mitotic activity takes
the
cells
also
place
become
more
than in
there
larger
rich in
and
cytoplasm,
but later
starch,
3
(fig.
The middle
stretch
they
of the seed and
that
the
of the i.i.
are
plane,
layers
become very
to
so
large,
tender tissue. The cells
a
seed. This
growing
plane
the transversal
B).
and thus form
thin-walled,
in the median
frequently
seed becomes flattened
developing
originally
23
LINUM
TESTA OF
poor
adjacent
in
to
the endotheliumlongest remain cytoplasm-rich. The subdermal cells of the i.i. do
not
enlarge
direction
the
to
same
perpendicular
the
to
remnants
and
enchymatous
3
(fig.
are
the
and these cells stretch
the increase in
following
only
ones
discernible in the
in the
girth by
of the middle i.i.
cell
numerous
become sclerotic. The o.i. is
layer
to
seed
where it may become about four cells thick
the inner cell
the
most
layer (fig.
do
layer
outer
B).
layer only scarcely
seed
during
of the o.i.
formation of these
by
stance
the
is
All cells of the o.i.
layer
time the
presumably
The
The
mature
seed-coat is formed
slime-producing
one
(jigs. JE, 4C, D, E).
the
polygonal
layers
edge
exhibit
a
positive
immediately
are
its
maximum
outer
before full
all
of the
the
cells
the
a
are
3
extent
surface
maturity
D). During
starch
the
amyloplasts
have
grains
slime-producing
to
sub-
(fig.
coat
hardly
to
even
not
the
4
C)
(fig.
4
red,
twice
and
same
or
structureless,
separating
are
wall
state
When hand
or
in absolute
opaque layer.
to some
When
extent,
walls become visible. In
of these cells in
which
they
mucilaginous
water
a
is facilitated
to
dry
sections
radial direction
three times their original
passively stretched,
throughout:
whereas
strongly.
dry
discernible. Addition of
swelling
and
outermost
but the first-formed wall
more
observed in the
a
The
D).
outer-
is the
cuticule poor in cutin
rugose-plicate
cells is
the
by
layer
the alcohol the slime cells swell
thickening layers
lumen is
and
seed-coat
elongate
cells appear as
added
which the cells may stretch
become
a
mucilage
cuticle stain
sudden and considerable
cell walls
the whole of the o.i.
conspicuous
microscopically
gradually
of the cells
a
considerable
On the
Immediately
reaction with ruthenium
below
that the individual
causes
by
most
shape
mucilage-forming
little water is
so
to a
metabolised when the
in the other parts of the seed
alcohol the
most
and those of the inner-
the cells still contain numerous
which is covered with
The
of the seed
sections of linseed
a
enlarge
the
divisions of
seed
mature
innermost layers of the i.i. The
layers
B,C.D)
deposited.
3.4.
along
more
whilst
of the seed those of
edge
ones
deposited (fig.
are
reaches
thickening
are
seed
by periclinal
amyloplasts.
is formed.
slime-forming layers
thickening layers
disappeared; they
the other
as
and become rich in
manifest cuticular
a
much
as
layers collapse
of the i.i. become
partly two-layered except alongside
Of the cells later forming the
so.
development
is attained the first
but
3
stretch
not
these
of which
anticlinal cell divisions (fig. 3
ultimately
edges
layers
direction of the
longitudinal
in the
C);
seed-coat between the scler-
mature
outermost
3 B,
(fig.
The other cells of the middle
pigment layers.
The nuclei of the cells of the
D).
oblong
are
also stretch
they
axis of the seed
longitudinal
cells also have thicker walls and
recognisable
do the other cells and
extent as
length.
by
the
by
The radial
presence of
24
F.
Fig.
4.
SEM
A:
seed,
B:
t.s.
photomicrographs of Linum
of seed-coat
C,D; seed-coat
E:
F:
about
(magnif.
as
(
x
seen
x
a
BOESEWINKEI
usitalissimum.
10);
500);
from above in
detail of cuticular structure
seed-coat after
D.
(x
the
raphal (x 1000)
and in
the
micropylar region (x 5000);
5000);
16 hrs. treatment with
HN0
3
.
Cuticle and outer wall have
disappeared(
x
500).
25
OVULE AND TESTA OF LINUM
Fig.
5. SEM
A, B,
A:
C;
photomicrographs of
photomicrographs of
cuticle
partly
removed
B:
shifted cuticle
C:
pleated cuticle (x
D:
seed-coat after a
40).
(
x
Linum usitatissimum
the seed-coat
(magn.
about
x
after
a
16 hrs. treatment with
HNO,.
250);
250);
2\
125);
days sojourn
in water with
formingprotruding folds
in
parts (magn.
about
x
26
Fig.
F.
6. SEM
photomicrographs
A:
seed-coat after
B:
dried
C:
sclerotic
layer
D:
sclerotic
layer
E;
pigment layer
F:
anticlinal wall
16 hrs. in H
mucilage on
seed-coat
of seed-coat
of Linum
0-cells
usilatissimum
intact
2
(
after removal
seen
from the inside
(x
seen
from above
500);
of
pigment cell
(magn.
about
500);
x
(
x
with
of o.i.
(x 500);
250);
pits ( x
2500).
x
1000);
D.
BOESEWINKEL
OVULE
AND
TESTA
27
OF LINUM
which become almost
numerous, minute folds in these walls
ed
(fig.
out
3
The folds
E).
rich slime-cells desiccated
of the slime-cells
ing
nected with the
curl up
under
causes
the ruptures in such
seeds have been
a
in
the
along
coat
sharp edge
not
does
detached from the
is
the
basal,
rest
adhere
to
in
or torn
number of
a
only through
When
recognisable.
is initiated
the
by
micropylar
area.
the other parts of the seed
sojourn
a
treatment
often
the
especially
peripheral parts
come
directly
The seed-coat
as
a
cell
outer
appearance, which may be
and
layer
expected
on
wrinkling,
to
so
that
the
cuticle has also
of the cell walls have
disap-
contain all of the slime
swelling capacity (Jig.
5
mucilage completely.
dried
subsequently
may have
a
ropy
of its great adhesive power.
account
whole consists of five
the cuticle
of the anticlinal
into view. Free hand sections
substance in the intact cells which retain their
Slime diffused out of the
causes
when the
for about 16 hrs.
water
wrinkled and
finely
rupturing
concomitant with
obliterated,
in
are
with HN0
by
for about 16 hrs in
pretreated
Seeds treated with diluted nitric acid have lost their
A).
con-
sometimes
they
for several hours
water
of the seed in the
of the seed
suberised cell walls
of such seeds after
producing
that
3
shifted. After the cuticle and the
the
so
germination
of whole seeds
usually
cell pattern becomes
peared,
tightly
coat
Especially
cell walls. This
epidermal
water-
from the slit and later the rootlet appears.
5 A-D, 6A).
fully
original
long enough
10 % nitric acid reveals that their cuticles
(figs.
become
places,
cell pattern is still
original
water
SEM observation of the seed
water or
torn
in many
of the seed. The slime exudes
sharp edge
pigment layer (which
coat) protrudes
layer
shows that the cuticle is lifted
way that the
soaking
of the seed
splitting
the
originally
ruptures in the cuticle, which usually remains
Observation of whole seeds soaked in
near
smooth-
completely
when the
originated
seed maturation. The strong and sudden swell-
cell wall
stereo-microscope
places, especially
The
during
peripheral
together.
a
presumably
viz.
well-distinguishable layers
(fig.
3
E);
1.
The
layer
outer
of
whose
cells,
mucilage
screened from the remainder of the seed
2.
The innermost
often referred
slime-forming
the
the
by
name
of
cells”
“ring
substance
basal, suberised
of somewhat flattened cells of the
layer
to
by
owing
o.i.,
is well
cell wall
parts.
whose cells
are
their suborbicular
to
outline in surface view.
3.
The
ted
outermost
as
layer
of the i.i.
Between the fibres there
pits
B).
which
The
cells
give
cell walls
protrude into
discernible in
are
the
seen
are
sections
sclerenchymatous
and the
protrusions
are
(fig.
(figs.
elements
more
are
cells orien-
(fig.
6
C).
grooved
appearance
3
6
E,
so
C);
4
that the latter has
the protrusions
B). Along
relatively larger
the
and
(Jigs. 3E,4
peripheral ring
are
narrow
more
an
undulate
also
edge
clearly
of the
thick-walled,
elongate.
completely compressed
situated
a
thinner than the lateral ones. The
in surface view
seed the
layers
numerous,
lignified
direction of the seed
often somewhat longitudinally extended
sclerenchymatous layer
transverse
The almost
of thick-walled,
longitudinal
the inner surface of the cell wall
tangential
appearance when
4.
consisting
fibrous elements in the
immediately
and
below the
partly
resorbed remains of the cell
sclerenchyma layer.
These appear
as
a
28
F.
striation
5.
crossing
the fibrous elements almost
“
been dubbed
reason
The innermost
somewhat
{fig. 6 E).
Querzellen
of the i.i. known
layer
The cell walls
The
degenerated
no
When the
is
saw-edged.
in surface view under
seen
The
pigment
is
layer
tightly
The
plane.
mature
seed.
sharp edges
of the
is fairly
and
large
bundle is
raphal
According
The
and
amphicribral
Netolitzky
to
seed. The
straight.
is
there is
(1926),
of the chalaza.
much flattened, 4x2x1
laterally
the
of
consisting
and
filled with tannic substances
pigment layer
starch-containing embryo
fully
corky plugging
faintly pitted;
look
pits
the median
in the
The seed is
pigment layer
becomes thinner towards the
endosperm
lie in
the
as
completely
oleaginous endosperm.
oleiferous and but little
cotyledons
cells
and have for that
6 D.
fig.
see
BOESEWINKEL
somewhat thickened and the anticlinal walls contain
are
these
light microscope
connected with the
perpendicularly
(cross-cells);
tangentially elongate
elongate pits (Jigs. 3E,6 F).
the
”
D.
is
pigment layer
responsible
mm,
of a
shiny
brown color, and
for the brown coloration of the
testa.
The seed-coats of other Linum
species
as
far
as
seen
do
not
differ much of that
of Linum usitatissimum.
4.
DISCUSSION
The
ovule
regards
(1970)
of Linum
usitatissimum has
the presence of
there is
reduction of
a
parietal
within the
tendency
the
cells.
nucellar
According
family
which
tissue,
slender
a
and
Radiola linoides
According
layers
1937)
to
cells
it
is
Corner
thought
brought
about
by
two-layered
the other
two.
is
(1976)
to
be
to
a
are
the i.i. of the
out
layers
of the 9
clusion
in favour
was
arrived
although they
characters.
of
endothelium and
at
an
by
and in
(Rao)
tenuinucellate.
to
family
Radiola linoides
status
a
12 cell
According
by
species
himand
theo.i. is
is
Rao the
3-layered
in
of
to
Rao
a
also in Anis-
are
additional
genus Linum. The
(1972)
ovule
the
consistently
occurs
on
of
arguments
same
anatomical
of Linum have retained
erroneously
to
according
are
in
enlargement
(Mauritzon).
solid i.i.
of the
described the
mistook the i.i. for the nucellus and
also reports that
studied
obturator
Heimsch & Tschabold
(1891)
progressive
from 3
that any
pluricellular archespore
advanced
believe thatseveral
Brandza
a
tenuinucellare
and Linum perenne
alone.
layer
representatives
The obvious corollary is that in this
Hugonia (Rao)
a
completely
of cells thick and
The presence of tenuinucellateovules and
pleading
even
Linaceae may be
divisions of the innermost
in 7
as
Also in Anisadenia saxatilis ovules
(Rao 1968),
1934)
to
variable
and Narayana
be thicker in the herbaceous forms (see also Crete
familial characteristic. A
adenia and
found
is
and
(1968)
leads
even
derived condition. Corner
2-3
only
dermal derivation. The
constant
are
(Mauritzon
thick. Since it tends
Linaceae the o.i.
o.i. is
parietal
Rao
of the Linaceae towards
trend
condition in the herbaceous representatives.
with and without
nucellus
to
Linum
as
some
con-
grounds,
primitive
unitegmic.
concluded that the
He
pigment layer
OVULE AND
29
TESTA OF LINUM
is of nucellar
origin
also
(see
McLean & Ivimey-Cook
Guignard
(1964,
predominantly
nuclear
of Linum the
helobial type
of
Schurhoff
1919,
Linum mysorense does
haustorium is
Owing
gradually
particularly
the
from
and
the
swell,
in the other
as
of the
has
1884)
ve to
maintained
that
the
to
the
pharmacological
more
frequently,
as
of view
point
that when the seeds
In either
slime-forming layer
in
the
burst
1874a, b, Kobus
the
through
moves
molecules).
immersed
are
rents
1854, Sempolowski
mucilage
interstitial cavities between the
penetrate through the cuticle
(1945)
endosperm
studied.
protrudes through
cuticle. A smaller number (Hofmeister
(through
but the basal
1866-1867, Nobbe 1876, Collin &
opinion
substance
slimy
1901, Van Wisse-
of mucilage cells has been studied
and
In
severed from the
of linseed the seed-coatanatomy and
1855, Frank
are
species
is
other species
Dorasami & Gopinath
endosperm,
agricultural
an
Most workers
1904).
water
off
helobial
a
importance
1854, Cramer
(Hofmeister
in
cut
epidermal layer
mentioned before,
Perrot
have
to
endosperm
been recorded.
gradually
haustorium (Billings
a
1924). According
not
the economic
to
as
is
e.s.
in
repeated
was
some
formation has
endosperm
the basal part of the
remainder after it has functioned
lingh
error
but in the cultivated flax and in
(Rao),
addition, in these species,
p.
This
1893).
Within the Linaceae the
1484).
intact
cuticle
will ha-
case water
before any
swelling
protrudes
through
can occur.
The
present
confirms the
study
that
opinion
the
slime
not
retain
lesions in the cuticle.
Seeds treated for
slime is
apparently
soluble substances.
cosity
after
through
16 h with
10%
dissolved
or
nitric acid
has
Anderson &
been
Lowe
of linseed in diluted
boiling
Most workers believe that the cuticle is
can
escape
Haberlandt
According
and
also
(1947)
HC1,
so
found
the
mucilage;
any
transformed into
more
decrease of vis-
a
that the solution
readily
passes
filter paper.
the pressure built up
slime
do
chemically
elsewhere
rupturing
Wiesner
Koran
in
the
swelling
layer
leads
the cuticle
covering
rations and that
Hayward
simply
1927,
the
Hayward
tears
wall.
He
anticlinal walls
not
exist.
they
were
the
outer
wall
that the raised
rupturing
(1918)
outer
one
may expect
who
the
walls
may
of
preformation
so
that
that the
zones
have
perforations
already pointed
the cuticle would
studied hand sections
-
so
contain interstitial cavities
not
causes
relations in the sections of the cuticle
cuticles of whole seed
mucilage,
the anticlinal cell walls
over
a
Mangin (1893)
present
cites Haberlandt
on
so
if
the
rupturing
1938).
form both
suggested
the slime cells does
even
(1938)
pressure exerted
do
to
to
1867, Mangin 1893, Koran 1899,Tunmann 1913.
(1899)
outer
impermeable
slime
in the form of slime pores in the wall, but such
been observed and
cuticular
the
(Fluckiger
1918,
to
by
must
realising
altogether
find
that the
of the
that
perfo-
apart anyway.
not
burst. All workers
without
be
to
explained
rupturing
tear
out
or
of
never
that
increasing
very elastic
mentioning
the
tension
different from those in
more torn
places
in
sectioned
material.
The conclusion may be drawn that the cuticle is
impermeable
to
slime and
30
F.
somewhatelastic. The pressure of the
ing
of anticlinal cell walls in the
(Bouman
reveals that in
1974)
epidermides
some
species
the
outer
layer
of the i.i.
layer
at
are not
first forms
layer (Corner 1976,
micropylar
area
only,
the
sclerotised. Corner
he reducedfrom
a
“
distribution reduced
to
derive the
to
found
a
close
an
authors)
pigment
in
Hugonia (placed
differs
to some extent
a
from
the exotegmen becomes sclerotic in the
thick and its
The
In this
1976).
and endotesta cells
meso-
tegmen of Lineae may,
simple
are
therefore,
represented by Hugonieae”.
that Linaceae, Oxalidaceae and Geraniaceae are
related families (Engler
possible
fairly
states:
fairly generally accepted
(1922)
some
mesotestal construction
the Linaceae constitute
Corner
The seed-coat anatomy of
is
of the
into the exotegmen of theseed-coat, and
Linaceae:
testa
ballistic
family
endothelium which later becomes the
an
1968).
Rao
that of the other genera of the
It is
causes a
have also been recorded from
(Winkler 1931;
develops
separate family of the Hugoniaceae by
closely
of Oxalis the cuticle
common; they
and Radiola
Reinwardtia, Hesperolinon
partly
from the
protrude
of the seed minus its cuticle and part of the o.i. Within the
Linaceae slime
its inner
to
of this mechanism with conditions in the related Oxalidaceae
comparison
family
the ruptur-
causes
cells.
mucilage
dispersal
BOESEWINKEL
that the cuticle is lifted off in many
so
and may also become torn, which enables the slime
places
A
swelling mucilage layers
epidermis,
D.
1964 and
“old”
isolated
others). According
with
family
a
Netolitzky
patches.
to
Winkler (1931)
nowadays disintegrated
area
of
has shown that it is
(1926)
of Linum from that of the Geraniaceae. Hoeffgen
testa
be'tween
serological affinity
the
three above-mentioned
families. The similar ovular ontogeny in these families also suggests their great
taxonomic
and i.i.
Bouman
affinity (compare
of dermal derivation and
are
layers thick,
the i.i.
becoming 3-layered
divisions in the inner cell
layer
middle layer thus formed
(in
become thicker
Corner
to
latter
but of
more or
Linaceae,
(1923)
the seeds do
the
developed
less
not
have
star-shaped
Malpighiaceae,
Linaceae
are
are
usually
related. As far
as
places);
a
place
not
so
closely
Oxalidaceae.
from which
a
large
relationships
According
our
definite conclusions. A broader
tropical
genera, is
knowledge
knowledge
urgently required.
out
is thus
too
of these
to
between
Hallier
number of families have
(1979)
of the Linaceae is concerned,
Radiola and that
pointed
He is of the
related because in the
are
of the
are
chiefly
limited
opinion
not
one must
that the ontogeny of the ovule and the seed-coat anatomy is
Linum and
divisions in the
and the o.i. may
fibrous exotegmen.
united in the Rutales-Geraniales complex
the
cell
exotegmen consisting of fibrous elements
possibly
centre
two
by periclinal
layer.
in many directions. Frohne & Jensen
the families
by periclinal
some
both the o.i.
development
somewhat later stage
cells. He accepts manifest
and
the
an
1979):
the seed-coat structure,
on
have
that Linaceae and Geraniaceae
family
a
be followed later
his conclusions
of
early phases
at
divisions in the inner cell
by
(1976), basing
Boesewinkel
Geraniaceae only in
that both Linaceae and Celastraceae
opinion
1974,
in
to
that
necessarily
bear in mind
known from
permit
features, especially
more
of the
OVULE AND TESTA
31
OF LINUM
ACKNOWLEDGEMENTS
The author wishes to thank Dr. F. Bouman for useful discussions and Professor
his
and
interest, encouragement
assistance
of
J. Geenen
mr.
is
critical
translation
of the
original
Dutch
A. D. J. Meeuse for
draft.
The
technical
gratefully acknowledged.
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