FLORISTIC AND ECOLOGICAL SIGNIFICANCE OF COAL BALLS FROM LATE MIDDLE PENNSYLVANIAN STRATA OF WESTERN PENNSYLVANIA, U.S.A. (UNITED STATES)

342 coal balls or pieces of coal balls, representing a single concretionary mass occupying the full thickness of the original peat mass of a thin Allegheny Formation coal seam, were collected at the Derringer Corners locality, Lawrence County, western Pennsylvania, late Middle Pennsylvanian age.;The coal ball flora was composed of four major plant groups comprising about 30 genera common in the Pennsylvanian Euramerican coal swamps. By using a grid method of mapping, 13,203 cm('2) are quantitatively analysed from the middle peel of each of the coal balls or piece of coal balls. Lycopods were the dominant plants in this flora (66.5%); pteridosperms were of secondary importance (22.9%), ferns and sphenopsids were 8.0% and 4.6% respectively; and cordaitean plants were absent. Root systems contributed the most abundant part (57.7% of the total identifiable plant material in the coal balls) of the flora; stems occupied 31.7% of the plant mass (volume), leaves constituted 9.5%, and fructifications contributed only 1.5%. The aerial parts ("shoot") of the flora preserved in the permineralized peat mass have a ratio of 0.73 to the root (shoot/root ratio).;The abundance of lycopods is generally recognized as an indicator of a wet environment or habitat. However, the low shoot/root ratio infers relatively dry conditions in the coal-forming peat swamps at the Derringer Corners. The discrepancy of these two environmental indicators is discussed, and it is suggested that the regional climate was relatively dry, compared to that of some earlier coal-forming environment, but edaphic and perhaps geomorphic conditions resulted in local areas of wet habitat.;In the study of systematics of pteridosperms, two stem species (Schopfiastrum decussatum and Sutcliffia insignis), two leaf species (Alethopteris lesquereuxii and Alethopteris sullivantii), and one seed species (Pachytesta noei) are described and illustrated; the concentric leaf traces of Sutcliffia has been proved; one new stem species (Heterangium crossii) is designated. Morphological and anatomical variance of medullosan roots are also discussed. The technique transferring the entire epidermal tissue and cuticle of alethopterid pinnules from coal ball specimens, macerated by using EDTA solution, has been illustrated. Such preparations provide three-dimensional structure.