Protolepidodendron

Protolepidodendron

1. Protolepidodendron Presented by : Salvi Pinky P. M.Sc sem - 1 Paper - CBO : 402 Department of Life sciences, H.N.G.U ., Patan

2. Content Introduction General features Stem

3. Introduction The protolepidodendrales are a group of mostly small herbs known from the Devonian and Mississippian. As their name suggests, they are lycophytes , related to the giant scale trees of the Carboniferous. Unlike all other lycophytes however, the protolepidodendrales bore leaves which were forked at the tips.

4. A few are believed to have had multiple sporangia on each fertile leaf, such as the genus Estinnophyton , though three are some who suggest that this plant is actually a trimerophyte . The best known protolepidodendrid is Leclercqia , a plant which is known to have grown to at least a half – meter tall. Protolepidodendrales fossils are known from North America, Europe, China and Australia by the Middle Devonian, suggesting​ that they originated earlier. By the middle of the Carboniferous, they were extinct.

5. General features Protolepidodendrales are the group of fossil herbaceous homosporous plants​ having subterranean, aerial dichotomously branched axes, covered with ligulate or eligulate microphylls . The group had an apparently world wide distribution during Devonian and early Carboniferous periods​. They were probably ancestral to later lycophytes like lepidodendrales and selaginellales . Protolepidodendron represents the type genus of this group.

6. Baragwanathia longifolia from Silurian of Australia along with Yarravia is the oldest fossil which can be assigned under protolepidodendrales. The plant body of Baragwanathia longifolia is slightly larger than modern day laycopods. Sporangia are reniform, found in association with ordinary leaves present in certain area of stem representing cone of the plant.

7. Plants of protolepidodendron were of about 30 meters hight and 1 cm in diameter. Plant body consists of both prostrate as well as aerial axes. Like other laycopods whole plant body is covered with small leaves which are bifurcated at their apices, a unique feature of protolepidodendron leaves. Some of the leaves have redially elongated sporangia on their upper surface.

8. The ligules suggest that the protolepidodendrales are close relatives of lepidodendrales, selaginellales and isoetales,all of which have ligules as well. Leclerquia complexa is the earliest known lycophyte with ligules. Protolepidodendron specimen from the upper Devonian of New York, with cm scale.

9. Stem The​ stem is covered with slender leaves. Stems assigned to the protolepidodendrales range from 0.3 to 3 cm in diameter. Anatomically stem stele is star shaped, Action stele, similar to Asteroxylon. Triangular protostele is found in the stem which is uncommon among modern laycopods.

10. Protolepidodendron stem

11. References Botany For Degree Student Pteridophyta by : P.C.Vashishta, A.K.Sinha, Anil Kumar https ://acrobat.adobe.com https ://it.m.wikipedia.org https ://en.m.wikipedia.org

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