Beschreibung:
<jats:p>Numerous specimens of the pteridospermous pollen organs <jats:italic>Idanothekion glandulosum</jats:italic> and <jats:italic>Callandrium callistophytoides</jats:italic> are present in Middle and Upper Pennsylvanian petrifaction material, respectively. Several specimens of <jats:italic>Idanothekion</jats:italic>, previously known only in an isolated condition, are attached to foliage assignable to the monostelic seed fern <jats:italic>Callistophyton</jats:italic>. Proof of the affinities of <jats:italic>Idanothekion</jats:italic> allows this genus to be elevated from a form genus to an organ genus in the Callistophytaceae. The structure of the foliage and the mode of attachment of the <jats:italic>Idanothekion</jats:italic> specimens are like those previously described for <jats:italic>Callandrium</jats:italic>. Structural features of <jats:italic>Idanothekion</jats:italic> and <jats:italic>Callandrium</jats:italic> are compared, and the question of their identity is discussed. At present one basic type of pollen organ, borne on the abaxial surface of foliar pinnules, is known for members of the Callistophytaceae.</jats:p>