How early ferns became trees.
A new anatomically preserved fern, discovered from the basalmost Carboniferous of Australia, shows a unique combination of very primitive anatomical characters (solid centrarch cauline protostele) with the elaboration of an original model of the arborescent habit. This plant possessed a false trunk composed of a repetitive branching system of very small stems, which established it as the oldest tree-fern known to date. The potential of this primitive zygopterid fern to produce such an unusual growth form-without real equivalent among living plants-is related to the possession of two kinds of roots that have complementary functional roles: (i) large roots produced by stems with immediate positive geotropism, strongly adapted to mechanical support and water uptake from the soil; and (ii) small roots borne either on large roots or on petiole bases for absorbing humidity inside the false trunk.
Galtier
J
J
Laboratoire de Botanique et bioinformatique de l'architecture des plantes, FRE 2366 CNRS, Université Montpellier 2, C.C. 062, Place Bataillon, F-34095 Montpellier Cedex 5, France. galtier@isem.univ-montp2.fr
Hueber
F M
FM
D005075:Biological Evolution; D005580:Fossils; D010944:Plants / Q000033:anatomy & histology; D014197:Trees