This document summarizes the key characteristics of the seedless vascular plant Sphenophyllum. It belonged to the division Sphenophyta and was represented during the Carboniferous period. Sphenophyllum had jointed, ribbed stems and scale-like leaves arranged in whorls. It reproduced through sporangia borne on sporangiophores. The document describes the anatomy of the stem and roots. It also discusses several genera of reproductive structures classified under the form families Sphenophyllaceae and Cheirostrobaceae.

1. Dr. Jacob Thomas
Asst. Professor in Botany
Mar Thoma College, Tiruvalla
Seedless Vascular Plants

2. Sphenophyllum
■ Division – Sphenophyta
■ Class – Sphenophyllopsida
■ Order – Sphenophyllales

3. Sphenophyta
■ Commonly called horse tails
■ Known from Palaeozoic Era
■ Div. Sphenophyta represented by Equisetum
■ Plants have actual stem, roots and leaves
Sporophyte
■ Stem is jointed, nodes & internodes
■ Internode is hollw, it has ridges and furrows (ribbed)
Anatomy of stem
■ Protostelic (Sphenophyllum) or siphonostelic (Equisetum)
■ Absence of leaf gap as in Lycophyta
Leaves are small, scale like, arise in whorls, from the nodes
■ Branches also arise from nodes in whorls
Sporangia are born on peltate sporangiophores
■ Mostly homosporous (Equisetum) but some are heterosporous
Gametophyte dvpt. is exosporic and is green
■ Antherozoids are multiflagellated

4. Sphenophyllales
■ Originated in the upper Devonian
■ Reach climax during Carboniferous & lower Permian
■ Disappeared in lower Triassic
■ Stem is very delicate
■ Stem & roots showing secondary thickening
■ Leaves usually multiples of three present in each nodes & sessile
■ Strobili are contain whorls of appendages differentiated into sporangiphores &
bracts
■ Either homo or heterosporous
■ Represented by a single genus Sphenophyullum

5. Sphenophyllum
■ About 50 spp.
■ Sphenophyllum speciosum from Lower Gondwana of
India (Ramiganch series)
■ Morphology suggests that it was a prostrate trailer
with a partial aquatic
■ But anatomy suggests that it had a terrestrial habitat
and probably it may a climber
■ The ribs were not alternate as in Equisetum, but it
was continuous
■ Leaves were heterophyllous – this suggest that it had
an aquatic habitat
■ But heterophyllous leaves were intermingled (it
shows a doubtful habitat)
■ Dichotomously veined leaves suggest the
megaphyllous nature
■ So it was mistaken that it was a fern leaf
■ Roots – true, arise in whorls from the nodes,
adventitious

6. Compressions and permineralizations of Sphenophyllum show a
node/internode arrangement with whorls of wedge-shaped leaves

7. Anatomy of Stem & Root
■ Stem has prostrate with three radiating ridge
■ In root it was two
■ Xylem is exarch
■ Phloem is not preserved
■ Outside the phloem cambium is present
■ It was bifacial which is not present in woody pteridophytes
■ b/w protoxylem groups secondary xylem produced were large in size
■ But at corners, the secondary xylem cells were very small
■ Cortex – present cork cambium produces pteriderm
■ B’cos of the above anatomical characters it is suggest that it had terrestrial
habitat
Stem cross sections

8. Reproduction
■ The vegetative parts of many fossils of Sphenophyllum show similarity, the
cones of many species are different
■ So the reproductive structures in Sphenophyllales grouped in different ‘form
families’ and Genera
■ Family 1. Sphenophyllaceae Genera
1. Sphenophyllostachys (Bowmanites)
2. Peltastrobus
3. Sphenostrobus
4. Lithostrobus
■ Family 2. Cheirostrobaceae
1. Cheirostrobus
■ Family 3. Tristachyaceae
1. Tristachya
■ Family 4. Eviostachyiaceae
1. Eviostachys (Eviostachya)

9. Sphenophyllostachys (Bowmanites)
■ About 31 species are found
S. dowsonii
■ It is a small cone – 1cm in diameter
■ Strobilus has main axis
■ Nodes and internodes
■ Each nodes have sterile and fertile appendages
■ Sterile appendages is whorl of bracts
■ Bracts and sporangiophores are arranged in multiples of three
■ Bracts were fused to form a cup like structure
■ Each bracts bears a sporangiophore
■ These sporangiophores get branched at tip
■ And each branch of the sporangiophores carry one reflexed sporangium
■ The branching is of two types
■ In some it has a short median arm and two long side-branches
■ Others have two short median arms and a long distal arm

10. Sphenophyllostachys reomeri
■Similiar to that S. dowsonii except that each sporangiophore carried two reflexed
sporangia
S. acquensis
■Is the simplest of the cone
■Where at each node a whorl of free bracts are present and each bract has a single
sporangiophore with a single sporangium at their tips
S. majus
■Here the bract at a node is forked or dichotomised and at the axil of each bract, a
sporangiophore, each having 4 reflexed sporangia at their tips
S. fertilis
■It is a much complicated cone which was found detached from the vegetative parts
■But b’cos of the triarch arrangement of the wood in the axis they are assumed to that
belong to members of Sphenophyllum
■The cone is made up of six superimposed whorls of sporangiophores at each nodes
■Each sporangiophore at a node is subtended by a pair of bracts
■Each sporangiophore terminated in a group of branches which is about 16 in number and
each branching bearing two sporangia

11. Eviostachya
■Each cone had at its base a whorl of 6 bracts, above which there where whorls of
sporangiophores which were 6 in number
■Each sporangiophore divided in a characteristic way
■It was trichotomously divided into three and each branch is again divided into 9, with the
middle branch shorter
■Each branch ends in a sporangia and all together each sporangiophores carry a total
number of 27 reflexed sporangia and spinous projections from sporangiophores where
present
■Each sporangiophore stood vertically above each other which is characteristic of
Sphenophyllales
■But there were no bracts b/w whorls of sporangia
Cheirostrobus
■Has 36 sporangiophores in each whorl, subtended by the same number of bracts and each
bract has bifurcated tip
■It was obtained from Carboniferous deposits
■It is the most complex of all pteridophytic fructifications, that has been described