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THE APEX OF STIGMARIA (LYCOPSIDA), ROOTING ORGAN OF LEPIDODENDRALES
Author(s) -
Rothwell Gar W.
Publication year - 1984
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.1537-2197.1984.tb11954.x
Subject(s) - apex (geometry) , biology , pennsylvanian , anatomy , groove (engineering) , paleontology , elongation , botany , materials science , structural basin , ultimate tensile strength , metallurgy
An apical segment of Stigmaria ficoides recently has been located among specimens from Pennsylvanian sediments of Iowa, and provides the first indisputable structural evidence for apical organization and development in one of the most enigmatic of all tracheophyte organs. Toward the apex, the specimen tapers to a circular rim. Rootlet scars occur in a helical arrangement from the proximal end of the specimen to the margin of the rim. Within the rim there is a discontinuous groove that surrounds an irregularly concave apex. The specimen compares favorably with the rooting apex of young Nathorstiana specimens, and adds to our knowledge of homologies among lycophyte rhizomorphs with axial elongation.