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SULLITHECA DACTYLIFERA GEN. ET SP. N.: A NEW MEDULLOSAN POLLEN ORGAN AND ITS EVOLUTIONARY SIGNIFICANCE |
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| Authors: | Benton M Stidd Gilbert A Leisman Tom L Phillips |
| Institution: | Department of Biological Sciences, Western Illinois University, Macomb
Division of Biological Sciences, Emporia Kansas State College, Emporia Department of Botany, University of Illinois, Urbana |
| Abstract: | The pteridosperm (Medullosaceae) pollen organ Sullitheca dactylifera gen. et sp. n. is described from middle Pennsylvanian coal balls. The proximally fused units of the obpyriform compound synangium separate and extend distally as finger-like projections. Each projection contains 4–6 vertically oriented cylindrical sporangia arranged in pairs along the radius of the unit; each unit extends from the outer cover wall toward the center. The distal portion of the compound synangium is hollow as a result of the lateral separation of the centripetally and distally directed synangial units. About 40 tubular sporangia are present in all and dehiscence occurs along a lateral slit in each sporangium. Vascular strands are disposed around the periphery of the organ in addition to a single strand paralleling each sporangium. Two- or three-cell trichomes and stomata are present on the organ surface. Pollen of the Monoletes type is present. A paired row of sporangia in Sullitheca composing a synangial unit is considered the homologue of a paired row of sporangia in the more compact and highly evolved genus, Dolerotheca. |
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