Morphology, anatomy and phylogenetic studies on the Indian Mesozoic bennettitalean stems

Sharma B. D., Bohra D. R., Suthar 0. P. & Harsh R. 2013. Morphology, anatomy and phylogenetic studies on the Indian Mesozoic bennettitalean stems. Geophytology 43(1): 1-11. The present paper deals with morphology and anatomy of the extinct Mesozoic bennetitalean stems. In most of the cases, the stem surface is covered with rhomboid leaf bases arranged in spiral rows. The stems are branched or unbranched. The branching may be monopodial, sympodial or dichotomous. Vascular cylinder is either monoxylic or polyxylic with the wood manoxylic or pycnoxylic. Wood rays are long and uni- to triseriate. Tracheids have scalariform to multiseriate bordered pits on radial walls with circular or elliptical pit pores resembling those of cycadophytes and homoxylous angiosperms (Magnoliales). In phloem, sieve areas are circular, uniseriate and each with many sieve pores. Fructifications like Williamsonia, Wielandiella, Williamsoniella, Weltrichia and Amarjolia were associated with the bennettitalean stems. Phylogenetic relationship is suggested with cycadeoideas, cycads and vessel-less angiosperms.