ON THE “RESIDUAL” INTERPRETATION OF COASTAL FLORAS IN THE APPALACHIAN UPLANDS OF EASTERN UNITED STATES

Abstract

PR E S E N T I N G a discussion on coastal species in the Appalachian Uplands requires a survey of the work of Braun (I937a), Carr (I938a), Fernald (I93I, I937), Harshberger (I903), and Kearney (I900). In viewing the problem from aphytogeographical and ecological standpoint, these authors have sought to correlate the occurrence of coastal species in the uplands with the physiographic history of the province concerned. Such correlations combined with the disjunct ranges of the species have led to the residual interpretation. Geological evidence indicates that during late Cretaceous and early Tertiary the Appalachian Uplands were essentially reduced to a peneplane status, affording ideal conditions for a mesophytic plant growth. At this period the tropical groups were widespread in the North as shown by fossil record. Here the Coastal genera Stenophyllus, Xyria, Eriocaulon, Sarracenia, HIelonias, and Utricularia, etc., prevailed along the low meandering streams and in the swampy areas, until an uplift of the Schooley peneplane (Cretaceous) altered the conditions, in turn initiating a recession of the mesophytic and hydrophytic types to the available coastal strip. Mesophytes gave way to the developing xerophytes. However, relics of this flora still persist in segregated colonies in the Appalachian Uplands where ponds, bogs, and grassy meadows prevail. Braun (I937a) reports such relics as UJniola laxa (L.) B.S.P., Panicum longifolium Torr, Cleistes divaricata (L.) R.Br., Bartonia paniculata (Michx.) Robinson, Lobelia 2Vuttallii R. & S., and Orontium aquaticum L. from the Cumberland Plateau in Kentucky. All of these plants are to-day primarily confined to a narrow strip along the Atlantic Coast of Eastern United States, and show marked affinity with tropical groups. Of great interest is the report of Cleistes from the standpoint of extreme antiquity. To-day it shows a local distribution in the uplands, and has retreated only slightly to the Coastal Plain. Fernald (I937) comments on its slight occurrence in south-eastern Virginia in a region contributing such local plants as Xyris Curtissi Malme, Burmannia bifJlora L., and UJtricularia virgatula Barnhart. Its extreme antiquity is indicated by its scattered and disjunct range. It shares equal rank on thle relic list with ilelonias bullata L. which holds a similar, local distribution with slight intrusion in the coastal region. Following Fenneman (I928), Braun concludes that the Cumberland peneplane represents only the eroded and reduced Schooley peneplane (Cretaceous). Braun (I937 a) writes: rThe present known distribution of most of the coastal plain plants in the Cumberland Plateau coincides with the undissected remnants of the Schooley