Observed under LM in the present work were epidermal cells and stomatal
apparatuses of mature leaves in 37 species (50 samples) belonging to 19 genera and 6 sub-
families (Hamamelidaceae), of which 35 species (19 genera, 6 subfamilies) were also used for
observing under SEM cuticular membrane and wax sculpture, shape of stomata and stucture
of stomatal apparatuses of the lower epidermis.
(1) It is found that in the family cells of both upper and lower epidermis are tetragonal,
pentagonal and hexagonal or irregular; anticlinal walls are straight, arched, sinuolate and sin-
uate; stomatal apparatuses, which occur only on the lower surface, may be cyclocytic, stephano-
cytic, paracytic and anomocytic. All these characters of the leaf epidermis are of systematic
significance in the family (Fig. 1).
(2) Types of stomatal apparatuses are correlated to a certain extent with the pattern of
anticlinal walls of epidermal cells and other external morphological characters. In the majority
of cases, the groups, whose stomatal apparatuses are cyclocytic (Exbucklandioideae and Rhodo-
leioideae) and stephanocytic (Mytilaria Lec. and Tetrathyrium Benth.), all have straight or
arched anticlinal walls of lower and upper epidermal cells (except for Exbucklandia tonkin-
ensis with sinuate anticlinal walls of both upper and lower epidermal cells, and E. longipetala
with sinuate anticlinal walls of upper epidermal cells) (Plate 1:12, 13; 2:4), are all evergreen
trees or shrubs, and all have palmate veins and simple hairs (but Rhodoleioideae is pinnate-
veined or obscurely trinervious and has tufted hairs), indefinite floral parts and numerous ovu-
les, while the groups, whose stomatal apparatuses are paracytic (Disanthoideae, Chunia H.
T. Chang, Liquidambaroideae and Hamamelidoideae, which also has anomocytic type in small
portion of species) (Table 2), have sinuolate or sinuate anticlinal walls of upper and lower
epidermal cells (except for Chunia, Tetrathyrium, Corylopsis brevistyla and C. willmotiae,
which have straight and arched anticlinal walls), are mostly deciduous trees and shrubs, and
have pinnate veins and tufted hairs in most species, usually tetra-, or pentamerous flowers (ex-
cept for Liquidambaroideae, which has indefinite floral parts) and usually single ovule (but
Disanthoideae and Liquidambaroideae have numerous ovules).
(3) The subfamily Liquidambaroideae possesses polyporate pollen grains (Chang 1958,
1979), a circular vascular system in the midrib, at the centre of which is situated a secretory
channel (Huang 1982, 1986) and leaf teeth of the unique Altingioid tooth type (Li 1988) etc.
Based on these characters some authors tend to support the separation of the subfamily as a
family, Altingiaceae. The subfamily, however, shows strong differentiation of characters. For
example, in the subfamily, there are both evergreen and deciduous trees, palmate and pinnate
leaf veins, capitate, short-spicate and racemose inflorescences and half-interior and inferior ov-
aries. Furthermore, some characters in the subfamily, which are considered important for the
separation, are crisscross with those ih the other members of the Hamamelidaceae. Their sto-
matal apparatuses are similar to those in most groups of Hamamelidaceae (paracytic), and
Sycopsis sinensis also possesses polyporate pollen grains. The subfamily shares with the remain-
ing members of Hamamelidaceae many important characters, such as the presence of stipule,
two styles, 2-locular ovary, axial placenta, capsule. From the data available the separation of
the subfamily does not seem to be supported by adequate evidence, and it may well be a link
of the Hamamelidaceae with the related families.
(4) Considering the fact that the subfamily Disanthoideae and most members of the su-
bfamily Hamamelidoideae are of paracytic stomatal apparatuses and pentamerous flowers, the
present authors tend to agree with Huang's (1986) view that the subfamily Disanthoideae is
more closely related than the other subfamilies to Hamamelidoideae.
(5) Leaf epidermis of the family under study shows great diversity under SEM, even
within a genus in some cases, but it is generally stable at subfamily or genus level, and there-
fore SEM characters of the leaf epidermis is of certain taxonomic significance. For example,
Exbucklandioideae possesses ovate stomata. The cuticular membrane is annular around stomata
(Plate 3:3-6); most stomata are covered with lump-like cuticular membranes in Rhodoleio-
ideae (Plate 3:7,8,11,12); in Mytilaria the cuticular membrane appears lump-like, with a
minute-scaly waxy ornamentation (Plate 3:9); the cuticular membrane is striate, with large
scales on it in Chunia (Plate 3:10), and it is vermicular in Sycopsis (Plate 5: 9-11). Some
differences were also found among species in a genus, for instance, among the three species in
Corylopsis (Plate 4:12-14 and Table 2).
