Archaeopteris is the earliest known modern tree

Archaeopteris is an extinct plant which is of botanical interest for two re asons. It was the main component of the earliest forests until its extincti on around the Devonian/Carboniferous boundary(1-3), and phylogenetically, i t is the free-sporing taxon that shares the most characteristics with the s eed plants(4,5). Here we describe the largest group of anatomically preserv ed Archaeopteris remains ever found, from the Famennian marine beds of sout h-eastern Morocco(6), and provide the first evidence that, in terms of deve lopment and branching strategies, these 370-million-year-old plants were th e earliest known modern trees, This modernization involved the evolution of four characteristics: a lateral branching syndrome similar to the axillary branching of early seed plants; adventitious latent primordia similar to t hose produced by living trees, which eventually develop into roots on stem cuttings; nodal zones as important sites for the subsequent development of lateral organs; and wood anatomy strategies that minimize the mechanical st resses caused by perennial branch growth.