Of Lithocarpus, Castanopsis, Castanea, and Quercus only Lithocarpus frequently bears branched spikes suggestive of the primitive condition in the Fagaceae; the other genera sometimes have them in some individuals. Simple and branched spikes can occur on the same tree. Evolution of the simple spike is interpreted as the loss of branching capacity in the branched spikes. The Fagaceae show various transitional stages from perfect, entomophilous to imperfect, anemophilous flowers and from mixedsex to unisexual spikes. Complete separation of staminate from pistillate function into separate spikes and catkins occurs only in Quercus, which is also the only anemophilous member of these four genera. Lithocarpus is the least specialized while Quercus is the most specialized in inflorescence structure of the four genera. Pathways of inflorescence evolution in Castanea, Castanopsis, Lithocarpus, and Quercus have been proposed that identify Lithocarpus and Quercus as possessing the least and most specialized inflorescences, respectively (Kaul & Abbe, 1984). The specialized inflorescence character states of Quercus are associated with anemophily and the less specialized states in Lithocarpus, Castanea, and Castanopsis relate to their entomophily (Kaul, 1985). Kaul et al. (1986) suggested that the evolution of anemophily in Quercus [and probably also in another fagaceous species, Trigonobalanus daichangensis (Camus) Forman] was an adaptation for successful pollination in seasons of low pollinator activity in seasonal climates, for example, spring in the temperate latitudes. In such latitudes the anemophilous Fagaceae Quercus and Fagus flower briefly in the spring whereas the entomophilous Castanea and northerly species of Castanopsis and Lithocarpus flower over a longer period in early summer. Likewise, flowering peaks in entomophilous paleotropical Fagaceae (Castanopsis, Lithocarpus) coincide with maximum insect activity (Kaul et al., 1986; cf. Fogden, 1972). Quercus, which is anemophilous throughout its range, flowers at various times in the tropics but not in the wettest seasons. Further evidence of the functional aspects of these inflorescences is scanty, and therefore definitive answers to questions about the ancestry and subsequent functional evolution of fagaceous inflorescences must be sought through comparative studies of living and fossil taxa. In these genera the spikes and catkins usually bear numerous sessile, subsessile, or, in a few instances, pedunculate flower clusters that are variously called dichasia, cymules, or partial inflorescences. They are the only structures that presumably terminate in a flower in these four genera; all other structures-branches, rachises, spikes, and catkins-apparently terminate in a vegetative bud that may or may not be capable of further growth. The dichasia are surely derived by phylogenetic condensation and the ancestral inflorescences were probably thyrse-like or panicle-like. Some modem Fagaceae, most notably some species of Lithocarpus, produce branched spikes that are themselves aggregated into manybranched inflorescences of higher orders, resulting in the most complex floral displays in the family. The ancestral fagaceous inflorescence was no doubt more complex than any modem inflorescence in the family. Fey and Endress (1983) have advanced credible evidence that the cupule of the fruit is itself a product of condensation of dichasial branching systems. Further, Hjelmqvist (1948) interpreted some staminate flowers as pseudanthia. Kaul and Abbe (1984) suggested evolutionary changes in fagaceous inflorescences that included loss of syllepsis in both vegetative and reproductive shoots and separation of staI Research supported by National Science Foundation grants DEB-7921641 and DEB-8206937. 2 School of Biological Sciences, University of Nebraska, Lincoln, Nebraska 68588-0118. ANN. MISSOURI BOT. GARD. 73: 284-296. 1986. This content downloaded from 157.55.39.17 on Fri, 02 Sep 2016 04:42:57 UTC All use subject to http://about.jstor.org/terms 1986] KAUL-FAGACEAE INFLORESCENCES 285 minate from pistillate flowers in the total inflorescence. We also suggested that the catkins of anemophilous Fagaceae were derived from spikes of entomophilous ancestors and that there is a rough gradient of decreasing inflorescence complexity with increasing latitude. In our previous papers (Kaul & Abbe, 1984; Kaul, 1985) some complex fagaceous inflorescences were described and illustrated. Here I elaborate upon our work, illustrate additional examples of complex inflorescences, and provide further evidence for their interpretation as the least specialized forms among extant Fagaceae. It must be emphasized that even the least specialized extant forms are advanced for angiosperms as a whole, as evidenced by the presence of such extreme reductions as dichasia and cupules in every species.