Indian Williamsoniaceae-an overview

Abstract

The morphology, anatomy and phylogeny of the known extinct representatives of the family Williamsoniaceae from India have been overviewed. The family occurs in the Upper Mesozoic rocks and is represented by fronds, stems, male, female and bisexual fructifications. Though the fronds vary in shape, size and venation, all possess identical syndetocheilic stomata. The stems Bucklandia and Sahnioxylon show minor variations in structure of tracheary elements and are related with cycadeoideas and homoxylous angiosperms. The male fructification Weltrichia is built on very distinct and different plan than the seed-bearing fructification- Williamsonia, which has been derived from Cordaianthus. The bisexual fructification -Amarjolia is terminal and exposed like Williamsonia, while in structure and arrangement of microsporophyll resembles Cycadeoidea. Relationship among different organs is suggested and phylogeny of Williamsoniaceae is discussed.