Connection between Archaeopteris and Callixylon

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Science  20 May 1960:
Vol. 131, Issue 3412, pp. 1524-1525
DOI: 10.1126/science.131.3412.1524


Characters of two Upper Devonian genera, Archaeopteris, often considered to be a fern, and Callixylon, classified with the gymnosperms, have been recognized in a single specimen.