Modern and Paleocene Metasequoias: A Comparison of Foliage Morphology
Silicified peat from the Paleocene Fort Union Group in North Dakota has been studied using thin-section and peel methods. The internal structure of foliage identified as Metasequoia sp . is well preserved and is compared to the internal morphology of M. glyptostroboides foliage.
A single vascular bundle runs the length of the leaf, with a resin canal located abaxial to it, similar to M. glyptostroboides. Two additional resin canals occur in the mesophyll just above the lower epidermis, while M. glyptostroboides forms resin canals in the leaf margins. The vascular bundle is enclosed in a sheath of parenchyma and fibers with an incomplete ring of large endodermal-like cells located outside the sheath. No transfusion tracheids have been seen in fossil material. In the fossil material, preservation of the mesophyll is insufficient to differentiate it into palisade and spongy tissues. Palisade mesophyll is dorsi-ventral in M. glyptostroboides. No stomata are found on the upper epidermis but are well preserved on the lower surface. The degree of distortion of plant tissues during peatification is readily apparent.
KeywordsVascular Bundle Bundle Sheath Leaf Section Resin Canal Abaxial Epidermis
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