Geminitheca scotica gen. et sp. nov. : a Pteridosperm from the Lower Carboniferous of Dunbartonshire

Abstract

This article gives an account of the morphology of the ovulate cupules and microsporangia of Geminitheca scotica gen. et sp. nov., a new type of pteridospenn from the Lower Carboniferous of Dunbartonshire. The cupules are united in pairs and are borne in bunches at the tips of naked dichotomizing rachides. Evidence is put forward to show that the cupules are probably derived from a system of dichotomizing rachides modified to enclose terminal ovules. Each cupule contains two ovules similar in form to those of Calathospermum scoticum Walton, but differing in possessing a free integument. The elongated microsporangia also are borne in terminal bunches. The microspores have a cingulum.