Sieve Areas in Fossil Phloem

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Science  08 Dec 1978:
Vol. 202, Issue 4372, pp. 1081-1083
DOI: 10.1126/science.202.4372.1081


Phloem tissue of the Pennsylvanian fern Etapteris is described from permineralized specimens. Sieve elements possess regularly aligned sieve areas containing pores on the radial walls. The presence of these structures provides a basis for comparison with the phloem of living ferns.