42 1
J . Linn. Soc. (Rot.),56, 307, p . 421
With 1 plalea and 4 tezt-jguree
Print& in &.eat Britain
On Pityostrobus leckenbyi (Carruthers) Seward and
Pityostrobus oblongus (Lindley & Hutton) Seward,
fossil abietaceous cones from the Cretaceous
BY G. T. CREBER, F.L.S.
University CoUege School, Hampsteud
INTRODUCTION
“he present investigation commenced with the detailed anatomical study of two cones,
from the Albian-Crenomanian of the Agonne, loaned by the Director of the Ecole
Nationale Sup6risure de G6ologie Appliqub, Nancy. These cones had originally been
described by Fliche (1896)in broad outline and identified as C e d m oblonga, first recorded
by Lindley & Hutton (1836) from the Upper Greensand of Dorset. Flichc realized of
come that his cones also bore an immediate resemblance to Pinites leckenbyi (Carruthers,
1866)from the Lower Greensand of the Isle of Wight, but he did not use this name because
he considered Cedrua oblonga and Pinita leckenbyi to be identical and the former name
had clear priority. His decision as to the similarity of the two species was baaed on a
comparison of such of the internal structure a8 waa published at that time, comparison of
the external being ruled out on account of the considerable abrasion that Cedrua oblonga
had undergone. Pliche felt, however, that this abraded surfaee was quite consonant with
the kind of surface that would appear if Pinites leckenbyi had received similar treatment.
Stopes (1915) was quite opposed to this view; she considered that C e d m o b h g a had
considerable affinities to the modern genus Pinw and hence differed markedly from P.
leckenbyi which appeared to be truly allied to C e d m . There the matter has rested and it
has been tacitly assumed that C. oblonga was in fact an abraded pine-like cone, whereas
P. leckenbyi and Fliche’s cones were 80 obviously like those of the modern genus Cedrw
that no further diecussion appeared necessary.
To assess the true relationship of these forms, the anatomy of Pinita leckenbyi and
Cedw oblonga has been worked out in detail and an appraisal made of the evidence
obtained. Through the good offices of the curators of the Geological Museums of the
Universities of Oxford and Cambridge it has been possible to investigate the type specimens themselves.
So far in this introduction the original generic names for the specimens have been
used. In 1915 Stopes resuscitated Feistmantel’s (1874)form-genusPinostrobus for fossil
cones resembling those of the modern genus Pinua and erected Cedroetrobus for those
resembling Cedrus. Accordingly, C. oblonga was placed in Pinoetrobw on account of i t R
supposed pine-like qualities and P. leckenbyi was placed in Cedroatrobus. Seward (1919),
however, pointed out the dangers of closely allying fossil species with modern types, a
view recently reinforced by the work of Alvin (1953,1957).The latter found that certain
fossil con= possessed a mixture of the characters of the cones of modern genera and therefore to place a specimen in a modern genus may at once lead to obvious undesirable
anomalies. The modern practice follows Seward in placing a l l fossil Abietaceous cones in
Nathorst’s (1897)form-genusPityoatroha. Therefore C e d m oblonga and Pinita leckenbyi
are both placed in Pityoatrobus, the former being referred to as P. oblongw and the latter
a8 P.leckenbyi.
2-22
G. T.CREBER
422
DES~BIPT~ON
OF PITPOSTROBUS
LEOKENBPI
This description ie almost entirely baaed on the type specimen now in the oare of ,the
Sedgwick Muaeum, Cambridge; certain information, not obtainable &om the type, waa
obtained from the Nancy wnea whioh proved to be identical with the type in every
respect save size.
The type specimen is a large ovate cone 9.6 om. long and 6-0om. wide at the broadest
dimension. The two cones from fiance are smaller and rather more ellipeoidalin form, one
being 9.0by 4.2 cm. and the other 6-8by 4.0 om. They are all oalcareous petrifactions and
hence particularly suited to the preparation of cellulose peels,which were mounted entire.
I
/
...
br
brt
1 mm.
.
Text-fig. 1. Pity&robue Icckcnbyi. A, vertical seotion (tangential to the oone) through the fumd b m
of aseed-soaleoomplex~ndbreot-soale.
&r,braot-8oele;brt,breottraoe;i,innerlayerofhtegument;
2, resin canal; 8. space c a d by ehrinkege of the endoaperm; 819, eoleroteata;ah, shrunken endosperm. B. Longitudinal seotion through the proximal portion of a seed-ecale oomplex and ita
bmt-ecale; d, deoayed chalazsl t h e ; o, outer layer of integument; re, reah oavitiee; 88, dscale complex; set. w e d - d e oomplex traoe; at, eeed traoe; other labeh es for A. (Cameralucide
drawinge from oelluloee peels off the type speoimen.)
For the purposes of the original deaoription by Carruthera (1869)the type epeoimen waa
cut into two equal halves along the median vertical plane. The external surface of one
half and the internal surface of the other were figured in C m t h e r d s original paper, and
these figures are also to be found in Seward (1917). They show the charaoteriatic e x t e n ~ ~ l
form that haa led to the association with the genus Cedm. Thia appearance is due to the
fact that the spirally arranged scales are closely imbricabd so that only relatively small
areas of the abaxial surfaces of their thin broad tips are visible. Furthermore, these tips
bear minute vertical striations aa do the exposed parts of the scales of Cedm.
Fossil abietaceous m u from the Cretaceous
423
The massive a& is by no meam conatant in diameter along the length of the cone; it
is 1.6 cm. wide at the base and tapers to 0.3 cm. at the apex, at the mid-point the
diameter is 1.0 cm. The pith, of a similar form, is 0.6 cm. at the base, 0.35 cm. at the midpoint and 0.16 cm. at the apex. The seed-scale complexes consist of ovuliferous scales
arising in the axils of the bract-scales to which they are partly h e d ; the complete
bract-scale is 0.6 cm. long of which about 0.2 cm. is free from the seed-scale complex
(Text-fig. 1 B). The majority of the scales are set at right angles to the axis, although a
few at the base are set obtusely and a few at the apex acutely. The rhomboidal zone of
attachment to the axis of the fused bract and seed-scale complex is 0.7 cm. wide by
0.7 cm. high. The seed-scale complex is almost horizontal for about 1 cm. and on this part
lie the two seeds; the ascending portion being about 2.3 cm. long. The seed-scale complex
is 0-3cm. thick at the point where it diverges from the bract-scale; in the chalazal region
the thickness of the seed-scalebecomes reduced to 0.2 cm. (Text-fig. 1B), whilst at 1.3 cm.
from the actual apex the thickness increasee sharply to 0.3 cm. again. The m a of the
apex exposed on the surface of the cone is 2.8 cm. wide by 0.4 cm. deep. Measurement of
the changes in the breadth of the seed-scale in its various regions was not carried out on
the type specimen, but similar information was obtained from one of the Nancy specimens
(Text-fig. 2). This, however, is a smaller cone and therefore a factor of x 1.25 would have
to be applied in order to bring them inta line with the dimensions of the type. Two
winged seeds are set in each seed-scale,the wing portion of each is poorly preserved, aa is
the chalazal region, but the ellipsoidal sclerotesta, 0.9 cm. long by 0.4 cm. in diameter, is
well preserved (Text-fig. 1B).
Anatolny of the &a. The pith is composed of short cylindrical cells almost circular in
cross-section;they are relatively homogeneous, although some appear to have somewhat
denser contents. The vascular cylinder is 1.2 cm. in diameter at the base and tapers to
0.7 cm.; at the mid-point it is perforated by gaps associated with the departure of scale
traces. The xylem, largely secondary,is 0.3 cm. thick at the baae of the cone and 0.2 cm. at
the mid-point. It is composed of tracheids with small bordered pits; there are numeroue
uniseriate rays, but no resin canals. The phloem is not well preserved and the region is
largely occupied by secondary iron pyrites. Prominent in the cortex is a system of
twenty-one resin canals.
The vascular supply to the seed-sde complex and bract-scale leaves the axial vascular
system as a combined cylindrical trace of elliptical cross-section (Text-fig. 3 B ; P1. 1,
fig. 4). An oval gap appears in the axial xylem about 0.3 cm. high and 0-1 cm. wide.
AB the trace enters the cortex it is 0.33 cm. high and 0.26 cm. wide.
Anatomy of the seed-acde and bract-a&. On entry into the fused seed- and bract-scales
the cylindrical trace becomes wider and thinner at the sides (Text-fig. 3F; P1. 1, fig. 6)
so that the individual forms of the seed- and bract-scale trace gradually become more
evident. Finally the sides thin out altogether and the seed-scaletrace, now a flat band, is
entirely separated from the rounded bract trace (Text-fig. 3H). The system of cortical
resin canals gives rise to two lateral and a single adaxial resin canab in the seed-scale
(Text-figs.1A; 2A). The two resin can& of the bract-scale appear to arise independentky
of the axial system.
A section through the seed-scale shows that all the tissue abaxial to the flat band of
xylem is sclerenchymatous, at^ also is tho tissue of the extreme lateral portions where the
cells are strikingly large and thick-walled. These lateral portions retain their identity for
the greater part of the length of the seed-scale, although in the aecending part the cells
gradually come to resemble those of the abaxial sclerenchyma; the resin canals are derived
from the original lateral canals (Text-fig. 2B). The apical free part of the bract-scale is
very thin and is composed of large thin-walled sinuous cells in which are set the two
prominent resin canals. I n the amending part of the seed-scale the continuous band of
xylem gradually subdivides into a number of small rounded vascular bundles (Text-fig.
2E); in the chalazal region of the seeds two seed traces are given off and pass to them
GI.. T. CREBER
424
(Text-fig. 2D; P1.l,fig. 7).Just above this point a few resin canals appear in the ebaxial
sclerenchyma (Text-fig. 2E) and eventually in the thickest part of the scale there are
three distinct series of canals (Text-fig.2F), the central aeries alternate with the vascular
bundles and the last vestiges of the abaxial sclerenchyma lie between the two outer series.
Anatomy of the seed. The integument is differentiated into three layers of which the
sclerotesta, 0.04 cm. thick, is the best preserved (Text-fig. 1B). Internal t o this is a very
thin layer from whioh the megaspore membrane has separated by shrinkage in many of
the seeds (Text-fig. 1A). The outer layer is very badly preserved and itsdecay has produced
the very irregular surface of the seeds. Abundant resin cavities in the margin of the
solerotesta are present, mainly in the micropylar region whilst at the chalazal end a seed
trace is present (Text-fig.1 B). The, presumably, parenchymatous cells in this region have
decayed and only a thin outer layer remains which is continuous with the Wing on the
ascending part of the d - s c a l e . In some of the seeds an embryo is visible l@g in the
endoeperm (PI. 1, fig. 5).
Text-fig. 2. Pityoatzobua bckcnbyi. A-F, An aecending aeries of trsneverse eections of the need-scale
oomplex. c, cortex of the cone axis; d , deosyed ohslsml t k u e ; r, resin oanal; at, seed treoe;
U, v a ~ ~ u l s
bundle.
r
(Camera lucids drawinga from cellulose peeh off the type apemimen.)
r3yraanymY
Pityostrobus leckenbyi (Carruthers) Seward
Pinitea lechnbyi Carruthers, 1869, p. 2, pl. i, @. 1-6.
Cedrue leckenlyi (Sohimper, 1870, p. 299).
Pinitee lwkenbyi (Gardner, 1886. p. 246).
Ce dm obkmga (Fliche, 1896, p. 200, pl. vii, &p.1-6).
Cedrostrobue leckenbyi @ t o p , 1915, p. 143).
P i t y o e t r o h leckenbyi (Seward, 1919, p. 385).
E@b%dd 8p&$G d&l@w&
Abietuama cone, typically ovate in shape but some specimens ellipsoidal. Length
6.5-12-6 cm. and diameter 3.86-0 cm. Bract-scab small, the free part 0.2 cm. long, with
two rain canals. Seed-scaleespirally arranged and olosaly imbricated. Horizontal portion
1 om. long, ascending portion 2.3 cm. long. Exposed apical area 2.8 cm. by 0.4 cm.,
Fossil a b i e t a c m co12e9from the Cretaceous
425
minutely striated. Seeds, winged, 0.9 cm. long and 0.4 cm. in diameter; sclerotesta
0.04 cm. thick; resin cavities in the outer layer of the integument mainly in the micropylar region. Vascular supph~to the seed-scale and bract-scale united at first into a
oylinder, 0.33 cm. by 0.25 cm. in cross-section, giving rise to a rounded bract trace and
a flat seed-scale strand; single row of rounded vascular bundles in the upper part of the
seed-~~ale;
three resin canals in the base of the seed-scale,two lateral to the trace and one
adaxial to it; three series of canals in the upper part of the secd-scale, one close to the
abaxial surface, one close to the adaxial surface and one alternating with the vascular
bundles ; no resin canals in the abaxial sclerenchyma at the base of the seed-scale.
Type specimen. Cone with mounted cellulose peels in the Collection of the Sedgwick
museum, Cambridge. Horizon: Lower Greensand. Locality : Shanklin, Isle of Wight ;
K 2216.
Other specimens. Cones with mounted cellulose peels in the Collection of the Ecole
Nationale Sup6rieure de Wlogie AppliquBe, Nancy, France. Horizon : Albian-Cenomanian. Locality: Clermont en Argonne.
DESCBIPTION
OF PITPOSTROBUS
OBLONGUB
The type specimen, a water-worn cone from the Upper Greensand of the Dorset coaat,
is 6-78 cm. long and 3.0 cm. in diameter at the widest point. Clearly the specimen wm
origindly much longer aa there are incomplete seeds at both the base and the apex;
Qo
QO
E
F
0 0
c
D
m
H
1 mm.
U
Text-fig. 3. Pdtyoetrobue leckcnbyi. A-H, A aeries of transverse sections of the veecular supply to the
seed-scde complex and bract-male,showing the development of the independent treces from the
combined cylinder that a r k from the stele of the cone axis.
judging by the general shape of the axis and basal portions of the scales the outward
shapa of the cone might well have been ellipsoidal or even cylindrical rather than ovate.
When this specimen waa originally described it had been cut down the median vertical
plane and the two halves were figured by Lindley & Hutton (1835), these figurea are also
to be found in Seward (1919). For the purposes of this description cellulose peels were
taken from one of the cut sudaces, so aa t o reveal more of the internal anatomy.
The axh is relatively slender, being 0.6 cm. wide at the base ofthe specimenand tapering
slightly to 0.45 cm. at the apex. The pith is 0.28 cm. wide at the base and 0.16 cm. at the
apex. The angles between the scales and the axis are about 80 degrees, none of the scalee
G . T.CREBER
426
is set obtusely, but near the apex some arc more acutely arranged. The complete brad.
scale is 0.46 am. long, it ie partly fused to the seed-scale complex, but ita lateral margins
become free shortly after leaving the axis (Text-fig.4 J) and about 0.15 cm. of the tip is
completely free. The rhomboidal zone of attaahment to the axis of the fused bract and
seed-scaleis 0.5 cm. high and 0.4 cm. wide. The basal portion of the seed-scale is 0.2 cm.
thick and this decreases to 0.1 cm. in the chalazal region of the a&.
There me two winged
seeds on each seed-scale; the ellipsoidal sclerotesta of each is 0.6 cm. long and 0.26 cm.
wide.
The vascular supply to the seed-scalecomplex and bract-scale leaves the axial vascular
system as a combined cylindrical trace appearing in cross-section as an elongate ellipse
(Text-fig. 4C). A narrow slit-like gap appears first in the axial xylem about 0.3 cm.
high and 0.05 cm. wide. As the trace enters the cortex it is 0.65 cm. high and 0.12 cm.
wide (Text-fig.41)))the U-shaped bract trace then’separatos from the horseshoe-shaped
seed-scale trace and the open portions of each tend to close up slightly (Text-fig. 4F;
P1. 1, fig. 1). However, on entering the fused baees of the bract and aeed-sdes the bract
A
n
I
C
m
H
1 mrn.
U
Text-fig.4. Pityostmbw oblongus. A-I, A eeriea of trenaverm eectione of the vesoular eupply to the
md-scale complex and bract-male,showing the development of the independent traces from the
combined cylinder arieing from the eble of the cone axis. J , A vertical seotion through the partly
fused besee of B seedmale complex and bract-ecale. br, b r e o t - d e ; brt, brwt treoe; i , inner
layer of the integument; 0 , outer layer of the integument; T, reab anal; TC, reeh cavity; 8 , epece
caused by ahrinkage of the sakxosteeta; sCt, sclerotesta; 88, seed-ecde complex; 884 seed-soale
complex trace. (Camera lucid8 drawhgs from cellulose peele off the type speoimen.)
trace becomes rounded and the seed-scaletraca gradually opens out (Text-fig. 4G, H, 1;
P1. 1, fig. 3). The system of cortical reain canals in the axis gives rise to two lateral and
a single adaxial resin canals in the base of the seed-scale. Two canals axhe independently
in the bract-scale. There are no resin canals in the abaxial sclerenchyma in the base of
the seed-scale.
The integument of the seed ie differentiated into three layers, of which the sclerotesta,
0.025 cm. thick, is the beet preserved. Abundant large resin cavities are present in the
margin of the sclerotesta, both in the micropylar and chalazal regions (Pl. 1, fig. 2). The
cells in the latter region have largely decayed and often only the thin outer layer
remains, occasionally howover vestige8 of seed traces are discernible.
F08d
abietaceow, m
e
9 from the Cretaceous
427
Pityostrobus oblongus (Lindley & Hutton) Seward.
fiynOnYmY
Abies oblonga Lindley & Hutton, 1836, p. 137, pl. oxxxvii, figs. 1-2.
Elate oblonga (Unger, 1845, p. 199).
PiniteB oblonga (Endlichor, 1847, p. 20).
Pinites obbmgm (Unger, 1850, p. 358).
Abietitee oblongua (Coeppert, 1850, p. 207).
Pinites oblongw (Carruthem, 1866, vol. 3, p. 641; 1867, vol. 5, p. 12).
A b i e t i h obbngua (Gardner, 1886, p. 246).
Piniteo oblongue (Williamson, 1887, p. 189, p. ix, figs. 1-2).
Pinostrobw, oblongw, (Stopes, 1916, p. 135).
Pityoatrobua oblongw, (Sewerd, 1919, p. 387).
b
Emended specijk diaqnmis
A & b o u s m,
incomplete but probably originally 8-9 cm. long and 3.0 cm. in
diametm, cylindrical; axis, 0.45 cm.4.6 cm. in diameter. Bract-scale small, the free
part 0.16 om. long. Seeds, winged, 0.5 cm. long and 0.25 cm. wide; sclerotesta 0.026 cm.
thick; resin cavities throughout the outer layer of the integument. Vmcular a p p l y to the
seed-scale and bract-scale united a t first into a cylinder 0.66 cm. by 0.12 cm. in mosssection, eventually giving rise to a U-shaped bract trace and a horseshoe-shaped seedscale strand. Resin m d , three in number, in the bam of the seed-scale, two lateral to
the trace and one adaxial to it ; two canals in the bract-scale lateral to the trace.
Type specimen. Cone, in two portions O.U.M. K 10a and O.U.M. K 10 b, with mounted
cellulose peels, O.U.M. K lOb/P 1-14, in the Department of Geology and Mineralogy,
University Museum, Oxford. Horizon: Upper Gmnsand. Locality: Lyme Re@.
DISCUSSION
Clearly emerging from this investigation is the fact that thoee who believed Fliche's
cones to belong t o Pityostroh leckenbyi were correct, but, on the other hand, they were
not correct in assuming any special relationship to the modern genus Cedw. Those who
believed Pityostrobus obbngw and P . kchnbyi to be conspecific had a fairly broad, but
not excessive, view of the latitude of a species. Finally those who held that P . oblongus
had fundamental resemblance to cones of the genus Pknw, are shown to have been in error.
There are of course many points of resemblance between Pityostrobus oblongus and
P . lecken?yi, but there are ale0 points of difference and theae are important enough to
justify the maintenance of the individual specific names. The dSerences are concerned
with the vaecular supply to the seed-scale and bract-scale, with the form of the axis and
with the relative distribution of resin cavities in the seeds. I n the caae of P.oblongus the
combined trace divides to form two traces, one U-shaped and the other horseshoe-shaped,
whereaa in P. leckenbyi the seed-scale trace appeam aa a n almost flat band when it has
finally separated from the bract-scale trace. The form of the axis of P. 0b.bqu.a ia much
more cylindrical than that of P . leckenbyi, which tends t o be considerably wider at the
base. "he seeds of P.oblongus have abundant resin cavities distributed throughout the
outer layer of the integument, but those of P . leckenbyi have them chiefly in the vicinity
of the micropyle. These differences are not really within the limits of intraapecific
variation, and therefore P . oblongus and P . leckenbyi are maintained aa aeparate species.
The problem of attempting to establish the affinities of an Abietaceous fossil cone by
comparison with the anatomy of modern ones has been very thoroughly studied by Alvin
(1953, 1957). He has extended the work of Jeffrey (1906), who recognized two sections,
the Pineae and the Abieteae, in the Abietaceae. In the Pineae (Pinw,Picea, h r i x and
PsewEotsuga) resin canals are preaent in the cortex, the seed-scalee are pereistent, resin
G . T.CREBER
428
cavities are absent from the integument and there are no vaacular traces t o the seeds. In
the Abieteaa (Twga, Abiw, C e d m , Retehria and Peewlolarix) win canals are absent
from the secondary xylem (except in Abies), the seed-scales are deciduous (except in
Teuga and Keteleeriu), resin cavities are present in the integument and seed traces am
found.
Pityostrobus leckenbyi and P . oblongua cannot be placed satisfactorily in either of
Jeffrey’s scctions as they possess some of the features of each. They resemble the Pineae
in that they have cortical rcsin canals and their seed-scales were almost certainly persistent. They resemble the Abieteae in that they have traces to the seeds, resin oavities in the
integument and e distribution of resin canals in the base of the seed-scale is adaxial.
On balance they ppear to be more allied t o the Abieteae than to the Pineae, and the
suggestion that P . oblongus is a n abraded cone of a member of the Pineae now seoms most
unlikely in view of its anatomical structure. Resemblance of P . leckenbyi to the cones of
the genus Cedrw is purely in the external form ;there is a striking similarity, although the
apical pit of a typical Cedrua cone is absent. Internally most of the struotural anatomy
has a greater resemblance to that of a cone of A b i ~
or Picea than to Cedm, the cone
structure of which is highly specialized.
9
ACKNOWLEDGEMENTS
I wish to express my grateful thanks to the Director of the Eeole Nationale Superieure de
Gthlogie Appliquh (UniversitBde Nancy) for his kind permission t o borrow and section
the figured specimens of Pityoatrobw bckenbyi. I am indebted t o thc Curator of the
Sedgwick Museum, Cambridge, for the loan of the type specimen of P . leckenbyi and
t o the Curator of thc Geological Collections of the University Museurn, Oxford, for the
loan of the type specimen of P. oblongus. T am very grateful t o the Keeper of Geology,
British Museum (Natural History), for arranging for the loan of the specimens. Thanks
are duo to the %search Fund of the University of London for a grant to purchase large
slides and cover glasses for the mounting of the cellulose peels. I wish also t o record
my gratitude t o Mr P. R. Bell of University College, London, and to Dr K. L. Alvin of
Imperial College of Science nnd Technology for advice during the investigation and for
very helpfully criticizing the manuscript.
SUMMARY
An account ia given of hitherto unpublished details of the anatomy of the type specimen
of P i t y o s t r h k k e n b y i (Carruthers) Seward, and of two similar cones from the AlbianGnomanian of France. A comparison is made with P . oblongus (Lindley & Hutton)
Seward, and reasons arc given for maintaining these a.s eeparate speciea.
ADDENDUM
At the time of going to press the author’s attention was drawn to thc fact that an
account by Mlle. Christiane Lauvel of some more of Fliche’s specimens from the Museum
at Nancy was shortly to appear under the original name of Cedrue oblongs in the
Comptes Fhndues de la SociBG Gologique de France.
REFERENCES
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Plate 1
~]
G. T. c1mm::n
(Facing p. -l:!b)
Fossil abietacem
from the Cretacecuus
429
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EXPLANATION OF PLATE
Figs. 1-3. Pityoetrobua 0bkmgu.a
Fig. 1. Atransveree section of a pair of d - s c a l e and bract traces; two cortical resin canals are shown
out longitudinally.
Fig. 2. A longitudinal seotion of a seed showing the abundant resin cavities in the outer integument.
Fig. 3. A treneverse section through the fused bases of a d - s c a l e and its bract-male.
Figs. 4-7. Pityoatrobua hkenbyi
Fig. 4. A tramverse section through a combined seed-male and bract trace.
Fig. 6. A longitudinal section of a seed showing an embryo lying within the endosperm; to the left
are the closely a p p d cotyledons and the radicle is to the right.
Fig. 6. A transverse section of a seed-scale treco and a bract tram a t the point of separation.
Fig. 7. A longitudinal section of the chalaza1region of a seed showing a eeed tram diverging from the
vesculer tissue of the seed-male and entering the sclerohta.