Smith, Selena Y. , Stockey, Ruth A. , Nishida, Harufumi , Rothwell, Gar W. .
A blechnoid fern from the Middle Eocene Princeton chert: rhizomes, rachides and roots..
Several anatomically preserved rhizomes with adventitious roots and rachides of a blechnoid fern have been identified from the Middle Eocene Princeton chert of British Columbia, Canada. Rhizomes are preserved in growth position, bearing petioles that arise from all sides of the stem as well as diarch adventitious roots. Rhizomes are dictyostelic with five to six amphiphloic cauline bundles that are capped by sclerenchyma. The thin-walled ground tissue is incompletely preserved, but abundant small sclerotic nests are found throughout the pith and cortex. A few multicellular scales are borne on the rhizome, but are sparse and not imbricate. We have at least three orders of frond material including the stipes, primary pinnae, and secondary pinnae with laminae. Stipe anatomy strongly resembles ferns of Blechnaceae with an adaxial groove, two adaxial hippocampiform bundles and often six smaller circular bundles arranged in an abaxial U-shaped arc. Sections through the stipe show a central area of aerenchymatous ground tissue, an anatomy that suggests that these ferns were aquatic. In distal sections of the rachis, the vascular bundles are reduced to three or fewer. Neither trichomes nor scales have been observed on the rachides. While the anatomy of these vegetative parts suggests an affinity to Blechnaceae, the lack of attached reproductive material prevents us from placing the fossils in a modern genus. This new fossil material adds to the diversity of ferns from the Princeton chert that also includes osmundaceous, dennstaedtioid, and dryopteroid ferns.
1 - Ohio University, Department of Environmental and Plant Biology, Porter Hall, Richland Avenue, Athens, Ohio, 45701-2979, USA
2 - Chuo University, Faculty of Science and Engineering, 1-13-27 Kasuga, Bunkyo, Tokyo, 112-8551, JAPAN
3 - University of Alberta, Department of Biological Sciences, CW 405 Biological Sciences Building, Edmonton, Alberta, T6G 2E9, Canada
Presentation Type: Paper
Location: Maybird (Cliff Lodge)
Date: Wednesday, August 4th, 2004
Time: 11:15 AM