Anatomical variations in Indian Mesozoic pentoxylean stems

摘要

Sharma B. D., Bohra D. R., Suthar O. P. & Harsh R. 2013. Anatomical variations in Indian Mesozoic pentoxylean stems. Geophytology 42(2): 121 - 126. Anatomical variations are described in the pentoxylean stems collected from the Rajmahal Hills, Jharkhand. The fossil stem taxa considered here are Pentoxylon, Nipanioxylon, Guptioxylon and Purioxylon. In all these, stem surface is more or less smooth except for the dwarf shoots of Pentoxylon which have elliptical leaf bases in close spirals. The vasculature is polystelic and the secondary wood is pycnoxylic. Patches of sclerotic cells are seen in the ground tissue. In Pentoxylon, there are 5 - 7 endocentric steles surrounding a pentagonal pith. Nipanioxylon has 8 concentric or exocentric steles in a ring outside the pith periderm. Guptioxylon has 4-6 main concentric steles, endocentric or little irregular in shape; cortical and pith bundles are of various shapes and sizes. In Purioxylon, the pith periderm is surrounded by a ring of manoxylic bundles which are collateral, conjoint and endarch. Cortical bundles are of various sizes and have pycnoxylic wood. Phylogenetic importance of this study is also discussed.