B.SC HONS BOTANY SKBU PURULIA

1. Sphenophyllum
Dr. Sujit Ghosh

2. Sphenophyllum
• found in rocks ranging in age from Late Devonian to late Permian.
• The genus is characterized by delicate whorls of leaves arising from
nodes on thin, woody axes of various orders, and was a scrambling
plant that formed a ground cover of dense, multi-branching thickets
on both clastic and peat-forming substrates
• Leaves are heterophyllous, where morphology of the leaves depends• Leaves are heterophyllous, where morphology of the leaves depends
on the order of the branch to which they were originally attached.
• Whole-plant reconstructions do not yet exist for Sphenophyllum, in
part because rooting organs are rarely found in connection with
aerial parts of the plant.

3. OCCURRENCE
AND
DISTRIBUTION:
TYPE OF
FOSSIL:
These plants first appear
in upper Devonian period
and flourished until the
lower Triassic. These are
found in the Barakar
Coalfield and coalfields in
Bihar, Bengal, Satpura
basin and Sikkim.
It is the compression-
impression fossil.

4. EXTERNAL FEATURES
ROOTS: STEMS: LEAVES:
The roots are
adventitious borne
along the internodes,
rarely produced on the
lateral branch.
The stems are jointed
with non-alternating
ribs. The stem is delicate
in spite of secondary
thickening and thought
to be herbaceous
climbing stem. The
diameter of the stem
seldom exceed 1 cm in
diameter. It was
irregularly branched
(dichotomous), which
arise from nodes in
position alternating with
the leaves.
A whorl of 6-18 leaves
were present on each
node. The leaves are
constricted at the base
and expanded distally.
The leaves are supplied
with single vein, which
divided into two on
lamina. The leaves are
variously shaped.

5. Variation in Sphenophyllum leaf shape
•In S.emerginatum & S.majus the leaf was entire and wedge shaped.
•S.myriophyllum-dichotomously branched into several equal lobes.
•S.cuneifolium-bear both entire, wedge –shaped and deeply dissected
leaves.
Anatomically
The structure of leaf shows mesomorphic to xeromorphic features, although
these plants occurred within coal swamps. The chlorenchyma was reduced and
the dermal and hypodermal tissues were sclerenchymatous.

6. Internal structure
Epidermis
Periderm
Observed in
fossil records
Cortex
Well preserved
Massive
Sclerenchymato
us
Stele
Protostele-triarch
Xylem Is Entirely Made Up Of Tracheid, Having
Multiseriated Bordered Pit On The Lateral
Walls.
Secondary Growth Took Place From A Uni- Or
Bifacial Cambium, similar to that of
Carboniferous Lycopsids
Primary Phloem & Secondary Phloem
Consisted Of Thin-walled Sieve Elements. The
Sieve Cells Were Axially Elongated With
Tapered End Walls. The Sieve Elements Were
Of Relatively Small Diameter In The Areas
Opposite The Protoxylem Arms.

7. Reproductive structure
Reproductive organs of the Sphenophyllales consist of
aggregations of sporangiophores and bracts that
form cones or strobili.
Many types are known and they are preserved inMany types are known and they are preserved in
various ways.
Historically, the morphogenus Sphenophyllostachys was
used for all Sphenophyllum cones, but Hoskins and Cross
(1943) argued that Bowmanites has priority and should be
used instead.
Several other genera of sphenophyllalean cones have
later been introduced in recognition of the wide diversity
displayed by these structures (see Good, 1978).

8. Bowmanites- genus is regarded as homosporous. Strobilar consists of cone axis, whors of
bracts +subtended sporangiophore , sporangiophore bears sporangia, sporangia bear
spores
B.dawsonii -It is a form known from both European and North American
floras
•consist of a central axis bearing whorls of 14–20 bracts. alternate from
whorl to whorl Bracts are fusiform in outline and vascularized by a
single trace. They are inserted at right angles to the cone axis and
fused laterally to form a shallow disk. Toward the margin of the disk,
individual bracts are separated and upturned at their tips to overlap
the bracts of several whorls above
B. moorei
•is a relatively small cone with a maximum diameter of ∼4 mm
(Mamay, 1959b). Three bracts are produced at each node and laterally
fuse to form a disk. Each bract consists of a median fertile lobe flanked
by two sterile lobes. Bract tips do not overlap the whorl above. Each
fertile lobe produces two recurved sporangia
B. Trisporangiatus
•B. trisporangiatus, a cone 6 cm long A whorl consists of 18 bracts that
produce three sporangiophores each; spores are large (100–150 μm) and
trilete.

9. X= Axis.
The type of fructification described by Williamson and now
named Sphenophyllum Dawsoni consists of long cylindrical
cones, in external habit not unlike those of some
Calamitaieae. The axis, which in structure resembles the
vegetative stem in its primary condition, bears numerous
verticals of bracts, those of each verticil being coherent in
their lower part, so as to form a disc or cup, from the margin
of which the free limbs of the bracts arise. The sporangia,
which are about twice as numerous as the bracts, are seated
singly on pedicels or sporangiophores springing from the
upper surface of the bract-verticil, near its insertion on theBr= bract
Sp=sporangio
phores
Br=whorl of bract
upper surface of the bract-verticil, near its insertion on the
axis (fig. 6). As a rule two sporangiophores belong to each
bract. The sporangium is attached to the enlarged distal end
of its pedicel, from which it hangs down, so as to suggest an
anatropous ovule on its funiculus. Dehiscence appears to
have taken place at the free end of the sporangium; the
spores are numerous, and, so far as observed, of one kind
only. Each sporangiophore is traversed throughout its length
by a vascular bundle connected with that which supplies the
subtending bract