WHOLE-PLANT REGENERATION VIA EPIDERMAL CELLS IN THE AXIS OF THE EARLY DEVONIAN RHYNIE CHERT PLANT RHYNIA GWYNNE-VAUGHANII KIDSTON ET LANG

The Early Devonian Rhynie chert is an invaluable source for studying the morphology, ecology, and life cycles of early land plants, but information regarding morphological development in the Rhynie chert plants is sorely lacking. Serial petrographic thin sectioning of the Rhynie chert reveals asexual propagules developing from the epidermal cells in the axes of the plant Rhynia gwynne-vaughanii. Three distinct developmental stages recording the formation of stomata, rhizoids, apical growth, and vascular tissue were observed. Similar propagules are also found developing from hemispherical projections, also on the axes of Rhynia. The developmental pattern resembles that seen in somatic embryogenesis, a form of asexual reproduction that occurs naturally in extant plants as well as in in vitro, producing nutritionally independent plantlets from somatic plant cells. Our new observations on these propagules significantly contribute to a better understanding of how the tissues and organs of one of the earliest land plants formed. They allow us to compare the ontogeny of R. gwynne-vaughanii with that of extant land plant groups and demonstrate a form of asexual reproduction conserved over millions of years of plant evolution.