Ontogenetic and Anatomical Studies of the Flower and Fruit of the Fagaceae and Juglandaceae

Abstract

Two representatives each of the Fagaceae and the Juglandaceae[long dash]Quercus rubra, Fagus americana, Carya glabra, and Juglans mandchurica[long dash]were selected for comparative treatment; the conclusions based upon an examination of serial trans- and longisections of pistillate flowers and fruits at different stages in their development with careful analyses of their vascular organization. The pistillate flower of both the Fagaceae and the Juglandaceae is described as a somewhat modified ovule-bearing axis closely invested by a cupular envelope (the latter the product of conjoint growth of stem and carpels), the involucre also as cupular and consisting largely of fleshy axis. In the Fagaceae the involucre, as a ringlike swelling bearing numerous acro-petally developed scales, incompletely incloses a solitary floret or a 2- or 3-flowered inflorescence; in the Juglandaceae a greatly reduced involucre completely incloses the ovary of each floret and is united with it, forming the fibrous-fleshy indehiscent husk of the walnut and the 4-valved dehiscent husk of the hickory nut. The persistence in the seed-incasing body of the Fagaceae and Juglandaceae of inner and outer fleshy regions alternating with a bony layer suggests a pattern well defined in the gymnosperms, even to the cupule-inclosed seeds of the pteridosperms, except that both protective and nutritive functions have been to a large extent transferred from a highly differentiated seed coat to the ovary wall and involucral structures. The Fagaceae and Juglandaceae are seen as primitive groups but with many advanced characters; the Juglandaceae exhibiting a greater number of specialized features than do the Fagaceae, i.e., greater reduction in involucral and perianth parts as also in vascular supply to these members, combined with a bicarpellate, uniovulate ovary. No evidence was found either in Carya or Juglans to support the claim of a phyletic origin of the orthotropous ovule of the Juglandaceae from an anatropous or lateral type.