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

D. L. SMITH
Annals of Botany
New Series, Vol. 23, No. 91 (JULY 1959), pp. 477-491
Published by: Oxford University Press
Stable URL: http://www.jstor.org/stable/42907498
Page Count: 17
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Geminitheca scotica gen. et sp. nov.: a Pteridosperm from the Lower Carboniferous of Dunbartonshire
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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 pteridosperm from the Lower Carboniferous of Dunbartonshire. The cupules are united in pairs and are borne in bunches at the tips of naked dichotomizing rachidee. Evidence is put forward to show that the cupules are probably derived from a system of dichotomizing rachidee 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.

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