A subdivision of the division Pinophyta characterized by vessels in the secondary wood, ovules with two integuments, opposite leaves, and an embryo with two cotyledons.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



a subdivision of gymnospermous plants containing three orders: Ephedrales, Welwitschiales, and Gnetales. Each of these has one family and one genus, Ephedra, Welwitschia, and Gnetum, respectively. All three genera have common features: vessels in the secondary xylem and dichasial branching of strobile clusters (racemes), similar to the perianth cover around strobiles. They also have long microserrated tubes, dicotyledonous buds, and opposing leaves. There are no sap flows in the stems.

Many scientists recognize common origins for these three genera (probably from Bennettitales). Others believe Ephedra, Welwitschia, and Gnetum have different origins. Electronic-microscope research of the microspore layer of gneticae confirms their relationship to one another.


Takhtadzhian, A. L. Vysshye rasteniia, vol. 1. Moscow-Leningrad, 1956.


The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.