全 文 ：Received 16 Mar. 2004 Accepted 20 Aug. 2004
Supported by the Knowledge Innovation Program of The Chinese Academy of Sciences (KSCX2-SW-108), the National Natural Science
Foundation of China (39970056) and the Project of “Forward Research Field” from the Institute of Botany, The Chinese Academy of Sciences.
* Author for correspondence. E-mail: .
http://www.chineseplantscience.com
Acta Botanica Sinica
植 物 学 报 2004, 46 (11): 1261-1268
On the Anatomical Structures of the Lepidodendralean Stem
“Lepidodendron” tripunctatum from Coal Balls of Taiyuan
Formation in Shandong Province, North China
ZHOU Yi-Long1, LIU Xian-Wei2, WANG Shi-Jun1*, CHEN Gui-Ren3, TIAN Bao-Lin3
(1. Laboratory of Systematic and Evolutionary Botany, Institute of Botany, The Chinese Academy of Sciences, Beijing 100093, China;
2. North China Institute of Science and Technology, Beijing 101601, China;
3. China University of Mining and Technology, Beijing 100083, China)
Abstract: An anatomically preserved lepidodendralean stem is described from coal balls of the early
Early Permian or late Late Carboniferous Taiyuan Formation in Tao-Zao and Yanzhou coal fields from
southern Shandong, North China. The stem bears leaf cushions previously assigned into “Lepidodendron”
tachingshanense Lee, but is renamed as “Lepidodendron” tripunctatum Stock. et Math. based on the
morphology of the leaf cushion in this study. Comparison and relationship between “L.” tripunctatum and
other anatomically preserved lepidodendralean stems from the middle Late Carboniferous Euramerican and
the late Late Carboniferous or early Early Permian Cathaysian floras is made and discussed.
Key words: Cathaysian Flora; Taiyuan Formation; coal ball; lepidodendralean stem; “Lepidodendron”
tripunctatum ; anatomy
The coal balls in Coal Seam No. 16 of the early Early
Permian or late Late Carboniferous Taiyuan Formation in
Tao-Zao and Yanzhou coal-fields, southern Shandong
Province, yield abundant anatomically preserved
lepidodendralean plants. Among them one kind of leaf
Lepidophylloides hippocrepicus Wang, Tian et Chen and
two kinds of stem “Lepidodendron” pulchrum Zhang and
Diaphorodendron rhombicum Wang, have been reported
recently (Wang et al., 2002; Chen et al., 2003; Wang, 2004).
The third kind of lepidodendralean stem is reported in this
paper. It is studied in detail both on its morphology and
anatomy and is assigned into “L.” tripunctatum based on
the morphological features of the leaf cushion. The com-
parison between it and other known anatomically preserved
lepidodendralean stems from the Euramerican and
Cathaysian floras is made.
1 Materials and Methods
The material in this investigation includes two speci-
mens of the lepidodendralean stem. One of them was col-
lected from Beisu Coal Mine of Yanzhou Coal-field and is
numbered as YB-24. It is flattened with a long axis of 11 cm
and a short axis of 4 cm. The other one was collected from
Shanjialin Coal Mine of Tao-Zao Coal-field and is num-
bered as SS-26. It is also flattened and incompletely
preserved. Its long axis probably can reach up to 9 cm and
its short axis is 3.5 cm. In both specimens the outer cortex,
periderm and leaf cushions are well preserved, but the stele
is only preserved in YB-24, not in SS-26. No secondary
xylem is developed in both specimens. In order to obtain
the detailed morphological features of the leaf cushion, we
knocked the coal ball containing the specimen SS-26 and
the surface of the leaf cushion was exposed out. The peel-
ing method is employed in this investigation (Phillips et al.,
1976; Galtier and Phillips, 1999). The geological background
of the coal ball localities was introduced in detail by Guo et
al. (1990).
2 Description of the Specimens
Lepidodendron Sternburg sensu DiMichele, 1983
“ L.” tripunctatum Stock. et Math., 1939
(Figs.1-19)
1995 Lepidodendron tachingshanense Lee: Tian and
Wang, Pl. 58, Figs.3, 4
Diagnosis emended Leaf cushion vertically elongated
rhomboid with its top and basic angle more or less ob-
liquely truncate. Leaf scar large and asymmetrically rhom-
boid in shape with its upper sides slightly longer than the
lower ones and located at the middle and upper part of the
leaf cushion. Parichnos scars and vascular scar small and
circular. The most high-rising part of the leaf cushion just
below the leaf scar and the upper part of the leaf cushion
Acta Botanica Sinica 植物学报 Vol.46 No.11 20041262
(containing the leaf scar) inclined upward. Transverse pli-
cate weakly developed or absent. Stem siphonostelic with
mixed pith. Outer margin of the metaxylem smooth. Inner
and middle cortex unknown. Outer cortex 9-10 mm wide
and consisting of alternatively arranged radial thick-walled
cell bands and thin-walled cell areas. In tangential section
the outer cortex vertically anastomosing and in the center
of each thin-walled cell area being a vertically elliptical leaf
trace. The vascular bundle of the leaf trace consisting of an
upper horizontally elongated xylem strand, a lower cres-
cent-shaped sclerenchyma strand and a middle thin-walled
cell area probably of phloem. Vascular bundle sheath con-
sisting of small and nearly isodiametric parenchyma cells.
A mass of larger and loosely arranged parenchyma cells
enclosing the upper side of the leaf trace. Periderm consist-
ing of phellem and phelloderm. Phelloderm wider than
phellem and consisting of alternatively arranged tangential
thicker-walled cell bands and thinner-walled cell bands.
Phellem uniform and consisting of vertically elongated thick-
walled cells. Leaf trace and parichnos strand extending at a
horizontal course in the leaf cushion. Ligule large and stiff
with a height and a largest radial diameter of more than 1
mm and a largest tangential diameter of 600-800 mm. The
aperture of ligule pit very close to the top angle of the leaf
scar.
2.1 Stele
Specimen YB-24 is siphonostelic and the stele is flat-
tened with a long axis of 2.2 cm and a short axis of 1.1 cm
(Fig.14). The primary xylem is exarch with a smooth outer
margin or, in another word, the protoxylic poles are indistinct.
The diameter of the metaxylic tracheids increases inward.
The tracheids at the outer part are arranged contiguously,
while in the center of the stele the tracheids are arranged
loosely and mixed with small and thin-walled parenchyma
cells (Fig.15), thus the stem possesses a mixed pith. There
are scalariform thickenings with Williamson’s striations on
the metaxylic tracheid wall (Fig.10). The stele of specimen
SS-26 is not preserved.
2.2 Cortex
No inner and middle cortex have been observed in both
specimens probably because of their poor preservation.
Outer cortex is 7-10 mm wide in SS-26 and about 9 mm in
YB-24. It consists of alternatively arranged radial thick-
walled cell bands and cavities which represent the disap-
peared thin-walled cell areas (Figs.1-3). In SS-26, remnant
of parenchyma tissue sometimes can be seen in the cavities.
In tangential section through the outer cortex, the thick-
walled cell bands are vertically anastomosing (Fig.11). In
transverse section, the thick-walled cells are nearly
isodiametric and triangular, square or polygonal in shape
with their diameter increasing inward, from 40-75 mm to
50-100 mm or more in SS-26 and from 50-80 mm to 70-130
mm or more in YB-24. In longitudinal section, the thick-
walled cells are vertically elongated with their length de-
creasing inward, from more than 100 mm long at the outer-
most part to only 10 mm at the innermost part. Parenchyma
cells are nearly isodiametric in cross and longitudinal
sections. Within some radial thick-walled cell bands there
is a dark brown colored radial cell band consisting of smaller
and thicker walled cells than the surrounding ones in YB-
24. In tangential section through the outer cortex, there is
a leaf trace in each of cavity (Fig.11). The leaf trace is verti-
cally elliptical in shape and consists of an upper horizon-
tally elongated xylem strand, a middle horizontally elon-
gated area consisting of thin-walled cells that probably is
phloem and a lower crescent-shaped sclerenchyma strand
with its concave side upward. Vascular bundle sheath con-
sists of small and nearly isodiametric parenchyma cells.
There is a mass of loosely arranged and large-sized paren-
chyma cells that enclose the upper side of the leaf trace
(Fig.13). In radial section, leaf trace diverges at a very low
angle from the outer surface of the primary xylem of the
stem and is accompanied by some flattened sclerotic cells
at its adaxial side. When, however, the leaf trace enters the
outer cortex the sclerotic cells disappear. The leaf trace
extends at a nearly horizontal course in the outer cortex and
periderm till it enters the leaf cushion.
2.3 Periderm
Periderm consists of two distinct parts: phellem and
phelloderm. Phelloderm is 3.5-5.0 mm wide in YB-24 and
4.0-4.5 mm in SS-26. Phellem is weakly developed in YB-24
with the largest width of 0.5 mm. In SS-26 phellem is 1.2-
2.0 mm wide. Phelloderm consists of alternatively arranged
tangential thicker-walled cell bands and thinner-walled cell
bands and the latter are usually damaged into cracks (Fig.
16). Cells of phelloderm are nearly isodiametric or slightly
radially elongated in cross section. In radial section they
are vertically elongated with horizontal end wall (Fig.19).
Phellem can be roughly divided into two zones: the inner
one is in dark color due to the dark brown colored content
in cells; the outer one, however, is in light color and cells
are usually in poor preservation. In cross section cells of
phellem are slightly smaller than those of phelloderm and
are usually square in shape (Fig.16). In longitudinal section,
cells of phellem are vertically elongated with tapered end
wall (Fig.18).
2.4 Leaf cushion
2.4.1 Morphology and size Figure 4 shows the surface
ZHOU Yi-Long et al.: On the Anatomical Structures of the Lepidodendralean Stem “Lepidodendron” tripunctatum from Coal
Balls of Taiyuan Formation in Shandong Province, North China 1263
view of several leaf cushions of specimen SS-26. The leaf
cushion is roughly rhomboid in shape with its height slightly
larger than the width. Leaf scar is large and asymmetrically
rhomboid in shape with its basic and lateral angles about
90°and its upper sides slightly longer than the lower
ones. The most high-rising part of the leaf cushion is just
below the leaf scar so that the surface of the leaf scar is
inclined upward. There is a vertically elongated shallow
depression in the middle part of the leaf scar (Fig.4). In the
tangential section through the leaf cushion, the top and
Figs.1-9. “Lepidodendron” tripunctatum. 1-3. Transverse section of the stem, showing leaf cushion (LC), periderm (Pd), outer cortex
(OC) and stele (arrow). 4. Surface view of the leaf cushions, showing the shallow vertically elongated depression in the middle part of the
leaf scar (arrow). 5-7. Tangential section of the stem through leaf cushions, showing the form and arrangement of leaf cushions. Note that
at the left lower part of Fig.6 only the lower part of the leaf cushions can be seen, which means that the lower part is higher-rising than
the upper part of the leaf cushion. 8. Higher magnification of the vascular bundle (VB) in Fig.12, showing broad V-shaped xylem strand.
9. Higher magnification of a part in Fig.17, showing ligule (LG).
Acta Botanica Sinica 植物学报 Vol.46 No.11 20041264
basic angles of the leaf cushion of both specimens are ob-
liquely truncate which makes the leaf cushion into an un-
equal-laterally pentagonal or hexagonal outline (Figs.5-7).
The leaf cushion is 8-9 mm high and 6-7 mm wide in SS-26
and a little smaller in YB-24, 6 mm high and 4-5 mm wide.
They are contiguously and spirally arranged. In radial sec-
tion through the middle part of the leaf cushion of SS-26,
the maximum thickness, 3.5 mm, of the leaf cushion is just
below the leaf scar and the thickness gradually decreases
upward. Thus the leaf scar is inclined upward (Fig.17), which
is consistent with the morphological feature (Fig.4). When
making a series of tangential sections inward through the
leaf cushion we shall firstly cut the lower part of the leaf
cushion (Fig.6), which indicates that the lower part of the
leaf cushion of the present specimens is most high-rising.
2.4.2 Anatomy Several layers of cells beneath the epider-
mis are usually with secretory contents and in poor
preservation. Inside these cells are nearly isodiametric pa-
renchyma cells without content. The leaf trace enters the
middle part of the leaf cushion and extends outward at a
nearly horizontal course. Parichnos strand is just below the
leaf trace and in a V-shape with its concave side upward
when it enters the leaf cushion. There is a small mass of
thick-walled cells with very small diameter at the lower part
of the leaf cushion (Fig.12). When the leaf trace and
parichnos strand reach the base of the ligule pit, the
parichnos strand is divided into two and the mass of small
thick-walled cells is located between the two branches of
the parichnos strand. Leaf trace is semicircular or nearly
heart-shaped and consists of the lower arc-shaped or wide
V-shaped sclerenchyma strand and the upper V-shaped
xylem strand (Figs.8,12). Vascular bundle sheath is com-
posed of 1-2 layers of small and usually poor preserved
cells. Cells between the leaf trace and ligule pit are mostly
radially elongated and rectangular in shape among which
those close to the leaf trace with spiral thickenings are prob-
ably transfusion cells. Ligule pit is located at the outer part
of the leaf cushion and is very close to the surface of the
leaf scar (Figs.9,17). Ligule nearly fills up the whole pit and
the both are nearly in same shape. In radial section, height
of the ligule decreases from the outer side to the inner side,
so that the ligule is in a shape of a right triangle (Fig.9). In
tangential section the ligule is vertically elongated (Fig.12)
and similar to the shallow depression in the middle part of
the leaf scar in shape (Fig.4). The largest height of the ligule
is 1.0-1.7 mm in SS-26 and 1.0-1.2 mm in YB-24. The larg-
est radial diameter of the ligule is nearly the same as the
largest height in SS-26 and the largest tangential diameter
is 700-800 mm in SS-26 and 600-800 mm in YB-24. Ligule
consists of small and slightly vertically elongated cells
with dark brown content, so that the ligule is dark brown
colored as a whole. Ligule is located at the bottom of the
ligule pit by a broad base. The aperture of the ligule pit is
probably very close to the top angle of the leaf scar.
3 Comparison
3.1 Comparison with the Cathaysian lepidodendralean
stems in impression-compression preservation
There are several leaf cushions on the stem of SS-26
bearing the morphological features (Fig.4) which make it
possible to compare them with the Cathaysian
lepidodendralean stems in impression-compression
preservation. They resemble those of “Lepidodendron”
tripunctatum Stock. et Math. in possessing the asymmetri-
cally rhomboid leaf scar with its upper sides slightly longer
than the lower ones and its basic and lateral angles of about
90°. Furthermore, in some specimens of “L.” tripunctatum
(including the present specimens) there is a shallow verti-
cally elongated depression in the middle part of the leaf
scar (Fig.4; Gu et Zhi, 1974, Pl.9, Figs.7-10). “L.”
tachingshanense Lee is comparable to the present speci-
mens in possessing the unequal-laterally pentagonal or
hexagonal leaf cushion and large and rhomboid leaf scar,
which caused the stem to be assigned into the species by
some of the authors of this paper (Tian and Wang, 1995).
However, the rhomboid leaf scar of “L.” tachingshanense
has an equal upper and lower sides, and its basic angle is
obviously less than 90°and lateral angles are larger than
90°. Besides, there is not a shallow vertically elongated
depression in the middle part of the leaf scar in “L.”
tachingshanense (Li, 1963, Pl. 16, Fig.5, Pl.18, Figs.1-4).
Moreover, leaf cushions of some specimens of “L.”
tripunctatum in impression-compression preservation are
also more or less unequal-laterally pentagonal or hexago-
nal in form (Gu et Zhi, 1974, Pl.9, Figs.9, 10). Thus, we prefer
to assign the present specimens into “L.” tripunctatum
rather than “L.” tachingshanense.
3.2 Comparison with the other anatomically preserved
lepidodendralean stems
T h e a na t o mica l ly p r e se rve d E ur ame r i c an
lepidodendralean stems with vertically elongated leaf cush-
ion are assigned into five genera, including Lepidodendron
Sternburg sensu DiMichele, Diaphorodendron (DiMichele)
DiMichele et Bateman, Synchysidendron DiMichele et
Bateman, Paralycopodites (Morey et Morey) DiMichele
and Hizemodendron Bateman et DiMichele. Among these
genera, Diaphorodendron and Synchysidendron are closely
related to each other and belong to the same family
ZHOU Yi-Long et al.: On the Anatomical Structures of the Lepidodendralean Stem “Lepidodendron” tripunctatum from Coal
Balls of Taiyuan Formation in Shandong Province, North China 1265
Figs.10-19. “Lepidodendron” tripunctatum. 10. Scalariform thickenings with Williamson’s striations (arrow) on the metaxylic tracheid
wall. 11. Tangential section through the outer cortex, showing vertically anastomosing thick-walled cell bands. In each cavity there is a leaf
trace (arrows). 12. Tangential section through a leaf cushion showing ligule (LG), vascular bundle (VB), parichnos strand (Par) and a mass
of small thick-walled cells (arrow). 13. Higher magnification of a leaf trace in Fig.11, showing xylem strand (XS), V-shaped sclerenchyma
strand (SS) and probable phloem between them. The lower arrow indicates the vascular bundle sheath consisting of small and nearly
isodiametric parenchyma cells and the upper one indicates a mass of loosely arranged large-sized parenchyma cells that enclose the upper
side of the leaf trace. 14. Stele consisting of the outer contiguously arranged tracheids (X1) and the central mixed pith (P). 15. High
magnification of the mixed pith in Fig.14, showing large and elongated tracheids and small and poorly preserved parenchyma cells. 16.
Periderm showing phellem (Pm) and phelloderm (Pr). 17. Radial section through the middle part of a leaf cushion showing high-rising
lower part (large arrow) and tapered upper part (small arrow). 18. Radial section through the phellem. 19. Radial section through the
phelloderm. Coal balls: YB-24 (Figs.1,5,8,10-15); SS-26 (Figs.2-4,6,7,9,16-19). Scales: 1 cm (Fig.2); 5 mm (Figs.4,7); 4 mm (Fig.14);
3 mm (Fig.11); 2 mm (Fig.13); 1 mm (Figs.1, 3, 5, 6, 17); 500 mm (Figs.9, 12, 16); 200 mm (Figs.8, 15, 18, 19); 20 mm (Fig.10).
Acta Botanica Sinica 植物学报 Vol.46 No.11 20041266
Diaphorodendraceae (DiMichele and Bateman, 1992).
Both of them possess the distinct bi-zoned periderm con-
sisting of phellem and phelloderm. Phelloderm consists
of alternatively arranged tangential thicker-walled cell
bands and thinner-walled cell bands and the latter tends to
be cracks or holes when the specimens are in poor pres-
ervation (DiMichele and Bateman, 1992). However the
periderm of the other three genera consists of uniform
thick-walled cells or, in other words, does not differenti-
ated into phellem and phelloderm (DiMichele, 1980;
1983; Bateman and DiMichele, 1991). The periderm of
the present specimens is comparable to that of
Diaphorodendron and Synchysidendron in being dis-
tinctly bi-zoned or differentiated into phellem and
phelloderm. In Diaphorodendron its outer cortex con-
sists of alternatively arranged radial thick-walled cell bands
and thin-walled cell areas which, however, is weakly de-
veloped in Synchysidendron. In other three genera, i.e.
Lepidodendron, Paralycopodites and Hizemodendron,
the outer cortex consists of uniform thick-walled cells.
Thus the present specimens are consistent with
Diaphorodendron in the histology of outer cortex. The
type of stele is also one of the important diagnosis in dis-
tinguishing lepidodendralean stems. For example, only the
stem of Diaphorodendron possesses a protostele or a
siphonostele with the mixed pith. While the stems of the
other four genera, i.e. Synchysidendron, Lepidodendron,
Paralycopodites and Hizemodendron, typically possess
the siphonostele with parenchymatous pith. The present
specimens possess a stele with mixed pith, which is close
to Diaphorodendron. Thus, from the states as above, the
present specimens are comparable to Diaphorodendron
in the histology of periderm and outer cortex and in the
type of stele.
There are four species in Diaphorodendron at present.
Three of them, D. scleroticum, D. vasculare and D. phillipsii
were distributed in the Euramerican Flora and only one
species, D. rhombicum, was distributed in the Cathaysian
Flora. D. rhombicum is quite different from the Euramerican
species of Diaphorodendron in the morphology and
anatomy of leaf cushions. The leaf cushion of D. rhombicum
is in the form of diamond with nearly equal height and width.
The aperture of the ligule pit is very close to the top angle
of the leaf scar. Ligule is large and stiff with a length of
more than 1 mm and a diameter of nearly 1 mm (Wang,
2004). The leaf cushion of the Euramerican species is fusi-
form with a large ratio of height:width , from 2:1 to 4:1. The
aperture of the ligule pit is a little away from the top angle of
the leaf scar. Ligule is small and delicate with its length of
no more than 600-700 mm and width of 200-300 mm
(DiMichele, 1979; 1981; DiMichele and Bateman, 1992).
Obviously the present specimens are very close to D.
rhombicum in possessing the leaf cushion with small ratio
of height:width, large and stiff ligule and the aperture of the
ligule pit very close to the top angle of the leaf scar. The
only difference between D. rhombicum and the present
specimens is in the shape of the leaf scar: horizontally elon-
gated in D. rhombicum and rhomboid in the present
specimens. The Euramerican species of Diaphorodendron,
however, are quite different from the present specimens in
the form of the leaf cushion, the size of ligule and the place
of the aperture of the ligule pit as well as the shape of the
leaf scar. Probably there is a close relation between the
present specimens and D. rhombicum.
4 Discussion
“L.” tripunctatum was erected by Stockman and Mathieu
(1939) based on the impression-compression preservative
specimens from Hebei Province. Its geological age was from
Westphalian of the Late Carboniferous to the Early Permian.
However, the reported specimens of the species up to date
are all of impression-compression preservation. Thus our
investigation in this paper is the first report on the anatomi-
cal features of “L.” tripunctatum.
In some impression-compression preservative speci-
mens of “L.” tripunctatum there is a shallow vertically elon-
gated depression in the middle part of the leaf scar, however,
no other researchers have given the explanation to it and
we do not know how it has been formed. Now we can try to
give the explanation to this. In Figs.9 and 17 of this paper
we can see that the ligule pit is very close to the surface of
the leaf scar, which make the ligule pit easy to collapse and
form a shallow vertically elongated depression with the
same form as the ligule pit or ligule (Fig.12). However, in
other lepidodendralean stems such as D. rhombicum
(Wang, 2004), “L.” pulchrum (Chen et al., 2003) and “L”.
lepidophloides (Wang et al., 2002), between ligule pit and
the surface of leaf scar there is thick tissue which makes
ligule pit uneasy to collapse, thus no vertically elongated
depression was formed in the middle part of the leaf scar of
these stems in impression-compression preservation (Zhao
et al., 1980; Zhang, 1987).
U p to n o w, fo u r a na to mi c a l ly p r e s e r ve d
lepidodendralean stems have been reported from Taiyuan
Formation of North China and they are all distributed in
Tao-Zao and Yanzhou coal-fields, soutern Shandong
Province. They are “L.” pulchrum (Chen et al., 2003), “L.”
posthumii (Tian and Wang, 1995), D. rhombicum (Wang,
ZHOU Yi-Long et al.: On the Anatomical Structures of the Lepidodendralean Stem “Lepidodendron” tripunctatum from Coal
Balls of Taiyuan Formation in Shandong Province, North China 1267
2004) and “L.” tripunctatum (in this paper). “L.”
posthumii was published only by illustration (Tian and
Wang, 1995, Pl.58, Figs.1, 2) without any description and
comparison. The stem resembles the present specimens
in the histology of periderm and outer cortex and the type
of stele and only differs in possessing the leaf cushion
with a larger ratio of height to width, about 2:1. “L.”
posthumii is very close to Diaphorodendron but differs
in the shape of the leaf scar. It is usually smaller and trans-
versely elongated and located at the upper part of the leaf
cushion in Diaphorodendron but is larger and slightly
vertically elongated rhomboid and located at the middle
part of the leaf cushion in “L.” posthumii. It is worthy to
notice that “L.” pulchrum, “L.” posthumii, D. rhombicum
and “L.” tripunctatum, although they possess different
forms of the leaf cushion, are consistent with each other
in many anatomical features such as the histology of the
periderm and outer cortex and the type of stele. This means
that there may be a close relation between these stems.
There also is a close relationship between them and the
Euramerican species of Diaphorodendron, which is not
clear at present and need to be further studied in the future.
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