Survey and Morphology of Selected Groups of Early Land Plants

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Detailed investigation of morphologically and anatomically preserved Early Devonian plant taxa referable to trimerophytes or of problematical affinities is proposed. Characters useful in determining their possible relationships to major pteridophyte groups, refining taxonomic circumscriptions, and postulation patterns of divergence of structures or lineages should result. Specific projects include study of Psilophyton and Pertica- related plants from Canada and Germany in order to better characterize the trimerophytes and to develop hypotheses of phylogenetic relationships with other plant groups. Taeniocrad- type axes will be examined to determine number of taxa represented and to evaluate their relationships. Additional information about morphology and affinities of remains similar to the putative gameotophyte Caliculiphyton will be obtained. Several zosterophyll types continue to be studied for the purpose of better evaluating generic and species relationships. A variety of techniques, including degagement, maceration in acids, thin-sectioning, SEM observation, whole plant reconstruction, hypotheses of homology of structures, and phylogenetic analytical methods will be employed as appropriate. This research will expand and improve the array of characters useful in phylogenetic and evolutionary analyses, generate new hypotheses of relationships of some lineages, and contribute new information about the composition and diversity of early Devonian floras of southeastern Canada.