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STUDIES OF PALEOZOIC SEED FERNS: ANATOMY AND MORPHOLOGY OF MICROSPERMOPTERIS APHYLLUM
Author(s) -
Taylor Thomas N.,
Stockey Ruth A.
Publication year - 1976
Publication title -
american journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.218
H-Index - 151
eISSN - 1537-2197
pISSN - 0002-9122
DOI - 10.1002/j.1537-2197.1976.tb13215.x
Subject(s) - biology , pennsylvanian , phyllotaxis , appendage , botany , fern , genus , trichome , petiole (insect anatomy) , devonian , anatomy , paleontology , structural basin , shoot , meristem
The discovery of numerous specimens of the monostelic pteridosperm genus Microspermopteris in Pennsylvanian coal ball petrifactions from the Lewis Creek and What Cheer localities provides additional information about the anatomical and morphological variability within the genus. Specimens are now known up to 1.1 cm in diam that bear epidermal appendages in the form of variously‐shaped trichomes. The external surface of the stem is further ornamented by longitudinal flaps of cortical tissue. Petioles exhibiting a single C‐shaped vascular strand with abaxial protoxylem are produced in a 2/5 phyllotaxy. Large petiole bases that clasp the stem produce primary pinnae alternately. The presence of axillary branching appears similar to that reported in Callistopliyton and Lyginopteris. Triarch to polyarch adventitious roots, some with secondary tissues, are produced at both nodal and internodal regions. Of the currently recognized monostelic seed fern genera, Microspermopteris is most similar to Heterangium. Information is presented that supports current ideas regarding the evolution of the gymnospermic eustele from protostelic Devonian ancestors.