Lepidocarpon Sporangia from the Upper Carboniferous of Illinois

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Abstract
In a coal ball from coal seam no. 5, Harrisburg, Illinois (Up. Pennsylvanian), were found 60 Lepidocarpon sporangia separated from the parent axis and from one another. The sporangia, borne singly on the adaxial surface of the sporophyll, are distinguished by the possession of a massive wall differentiated into an outer protective layer and an inner nutritive layer. Within a sporangium were 4 megaspores, 3 of which aborted. The differential development displayed by the various specimens indicated an early selection of the chalazal megaspore as the functioning megaspore. With increase in size of the functioning megaspore there was a progressive decrease in the thickness of the megaspore membrane.

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