The characters of leaf epidermis (mainly epidermal cells, stomata, trichomes) have been
examined in 48 species of Quercus subgen. Cyclobalanopsis of the Fagaceae. The adaxial leaf epi-
dermis was investigated under light microscope. The epidermal cells of this surface are of two types
in terms of the outline of their anticlinal wall. One type is characterized by having straight wall, and this type has been observed in most of the species studied, while the other is characterized by having
sinuate or sinuolate wall, and this type has been found only in eight species, such as Q. blakei and
Q. hui. There exist two types of trichome-bases on this surface: in one type the bases are single-
celled, and this type has been found in most of the species studied, such as Q. oxyodon and Q.
augustinii; while in the other the bases consist of a group of cells, and this type has been found
only in nine species, such as Q. thorelii and Q. chungii. The abaxial leaf epidermis was investi-
gated under light microscope and scanning electron microscope. The epidermal cells and the
trichome-bases on this surface under LM are in morphology essentially similar to those on the adaxial
surface. The stomata under LM include three types: cyclocytic, subcyclocytic and anomocytic. The
stomatal density is of some diagnostic value to distinguish between closely related species, e.g. the
stomatal density in Q. glauca is higher than that in Q. schottkyana. Under SEM the stomata are
elliptical or roundish. The most noteworthy feature of the adaxial leaf epidermis is the trichomes.
Eight types of trichomes have been observed under SEM: simple-uniseriate, solitary, papillae, stel-
late, fused-stellate, stipitate-fasciculate, multiradiate and jellyfish-like. The first type, i.e. the
simple-uniseriate trichome, is glandular, other six types, i.e. the solitary, papillae, stellate,
fused-stellate, stipitate-fasciculate and multiradiate trichomes, are non-glandular, and the last one,
i.e. the jellyfish-like trichome, may represent an intermediate type in structure between the glandu-
lar and the non-glandular trichomes. Papillae are very common in subgen. Cyclobalanopsis although
in the Fagaceae they were previously reported only in a few species of Lithocarpus. The jellyfish-like
trichome, observed only in Q. sichouensis, is reported in the Fagaceae for the first time. The evo-
lutionary trends of trichomes are discussed. The trichomes seem to evolve toward the direction of in-
creasing complexity in structure. Papillae are considered as the pedomorphism of trichomes. From
papillae the solitary trichomes and then the stellate ones have evolved. The complicated trichome
types with more arms may be produced from relatively simple ones with fewer arms by means of vari-
ons fusion: several stellate trichomes are fused to form the fused-stellate ones by basal fusion, and
by the same way the fused-stellate ones to form the stipitate-fasciculate ones; the multiradiate
trichomes are formed by the stellate ones, in which the arms emerge in a variety of seemingly random
directions from a typically rounded common base. Based on the above results, it is considered that
the trichome features are of important significance for a better understanding of the infrageneric divi-
sion of Quercus and the phylogenetic relationships between this genus and the other genera in the
Fagaceae. The very common presence of papillae in Quercus subgen. Cyclobalanopsis and in a few
species of Lithocarpus may indicate that subgen. Cyclobalanopsis is a quite natural group on the one
hand, and may have close relationship with Lithocarpus on the other hand. The thin-walled, jelly-
fish-like trichomes found in Q. sichouensis are in structure similar to the “glandular” peltate
trichomes in Trigonobalanus, a genus generally regarded as the most primitive in subfam. Quer-
coideae, indicating that the affinity between subgen. Cyclobalanopsis and Trigonobalanus may be
closer than that between subgen. Quercus and Trigonobalanus.