The Phylloclade of Phyllocladus and its Possible Bearing on the Branch Systems of Progymnosperms

Abstract

The complex nature of the pinnate phylloclade of Phyllocladus, a genus generally classified under the Podocarpaceae, is described. This pinnate phylloclade probably represents a relic of a very ancient configuration and so far has been misinterpreted and erroneously designated. Comparison is made here between this structure and the telomic dichotomous branch systems of some Devonian Aneurophytales of the progymnosperms. It is suggested that the genus Phyllocladus probably represents an important link in the course of evolution between the progymnosperms and conifers. The simple foliage of the living coniferophytes is postulated as neotenic.