LEAF ARCHITECTURAL AND CUTICULAR ANALYSES OF EXTANT FAGACEAE AND 'FAGACEOUS' LEAVES FROM THE PALEOGENE OF SOUTHEASTERN NORTH AMERICA

Leaves of extant Fagaceae have been examined to provide information for the interpretation of putatively fagaceous fossil leaves. The cuticular morphology and leaf architecture, of over 300 species, representing all eight genera and about half the species in the family, were examined in detail. All extant Fagaceae have simple leaves of high rank with obliquely oriented tertiary veins, anomocytic and/or cyclocytic stomatal complexes and specific trichome complements which vary from genus to genus. Leaves of extant Fagaceae can be distinguished from those of other families when all characters are available. Most extant leaves can be identified at the generic level with little difficulty, however, a few foliar syndromes are common to more than one genus making assignment of these forms difficult if not impossible. Foliar information supports the segregation of Nothofagus into a separate family within the Fagales. Fagus leaves are distinct from those of other Fagaceae thus justifying segregation into the Fagoideae. Trigonobalanus appears to merit subfamilial standing as well. The leaves of this genus further suggest that division into two or more genera is warranted. There is considerable overlap in the foliar characteristics of the Quercoideae and Castanoideae yet reproductive features such as pollen morphology speak for retention of these two subfamilies. The impact of foliar data on other taxonomic problems has also been considered.; Information gained in the study of modern fagaceous leaves was used in the analysis of fossil fagaceous leaves from the Paleogene of southeastern North America. Two species possess foliar characteristics comparable to those of modern chestnuts. Three others were found to be closest to Quercus but quite distinct from any modern form. Of the five species treated here only the the latter three could possibly belong to the putatively ancestral "Dryophyllum" complex.