XVI International Botanical Congess

Progymnosperms collected at the Ashland Quarry of New York State have contributed significantly to our understanding of pre-seed plants. Additional material from this locality provides information about 5 branching orders of an aneurophyte possibly congeneric with Proteokalon. Anatomical detail of two orders has been preserved by petrifaction. Associated shale compressions reveal a shoot morphology displaying two distinct developmental patterns: thin lateral branches and short internodes, followed by more massive branches and expanded internodes. This is interpreted as a record of fluctuating conditions in the environment that led to growth retardation, and subsequent release from the inhibiting factor(s).