ON THE STRUCTURE OF CALAMOSTACHYS BINNEYANA FROM THE LOWER PENNSYLVANIAN OF NORTH AMERICA

The discovery of specimens of Calamostachys binneyana in Lower Pennsylvanan petrifaction material in North America has provided additional information about the structure of this calamitean fructification. The cones consist of regularly spaced alternating whorls of bracts and sporangiophores. Bracts are fused in a disc except at the margin where the individual units become free. Sporangiophores are inserted at right angles to the cone axis and bear four axially directed sporangia. The vascular system of the North American specimens differs from that in other reports of the taxon in the presence of twelve vascular bundles in the cone axis. Each sporangiophore is supplied by a single vascular trace that departs from one axial bundle. There appears to be no constant relationship between the number of vascular bundles and the number of bracts. Spores are spherical, thin‐walled, and of the Calamospora type. Relationships with other structurally preserved members in the genus are discussed in light of the diversity in structure demonstrated by the new specimens.