Jacob thomas mar_thoma_college_tiruvalla_
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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.
Jacob thomas mar_thoma_college_tiruvalla_
- 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 Bcos 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 bcos 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