Palms and the Origin and Evolution of Monocotyledons

Abstract

Past and Present taxonomic treatments and evolutionary analyses of monocotyledons have noted that unspecialized reproductive structures occur in some palms, but the size, inaccessibility, apparent and often real complexity of these plants have hampered detailed studies until recently. The most primitive palms are 14 or 15 apocarpous genera belonging to the Trithrinaux alliance in the coryphoid group. Apocarpy also characterizes Phoenix, a genus related to coryphoid palms but more specialized in some respects, and Nypa fruticans, a mangrove palm with a unique combination of primitive and specialized features. Distribution patterns, habits, leaf structure, germination, reproductive structures, chromosomes numbers, vessels, and vascular systems are described, as presently known, in these primitive palms, and their significance in the evolution of other palms, monocotyledons, and dicotyledons is evaluated. It is concluded that the palsm are not a morphologically unique and isolated group, as often postulated,...