A cladistic analysis of the families in the Hamamelidae is made in the present paper. As a monophyletic group, the subclass Hamamelidae includes 19 families, namely, the Trochodendraceae, Tetracentraceae, Cercidiphyllaceae, Eupteleaceae, Eucommiaceae, Hamamelidaceae (incl. Rhodoleiaceae and Altingiaceae), Platanaceae, Daphniphyllaceae, Balanopaceae, Didymelaceae, Myrothamnaceae, Buxaceae, Simmondsiaceae, Casuarinaceae, Fagaceae (incl. Nothofagaceae), Betulaceae, Myricaceae, Rhoipteleaceae and Juglandaceae. The Magnoliaceae was selected for outgroup comparison after careful consideration. Thirty-two informative character states were used in this study. Three principles, namely, outgroup comparison, fossil evidence and generally accepted viewpoints of morphological evolution, were used for polarization of the characters. An incompatible number concept was first introduced to evaluate the reliable degree of polarization of the characters and, by this method, the polarization of the three character states was corrected. A data matrix was constructed by the 19 ingroup families and 32 character states. The data matrix was analysed with the Minimal Parallel Evolutionary Method, Maximal Same Step Method (Xu 1989), and Synthetic Method. Three cladograms were constructed and a parsimonious cladogram (Length= 131)was used as the base for discussing the systematic relationships of families in the Hamamelidae. According to the cladogram, the earlist group differented in the subclass Hamamelidae consists of two vesselless wood families, the Trochodendraceae and Tetracentraceae. This result supports the concept proposed by Takhtajan (1987)and Cronquist (1981, 1988)that the Trochodendrales is probably a primitive taxon in the Hamamelidae. As in a clade group, the Cercidiphyllaceae, Eucommiaceae, Balanopaceae and Didymelaceae originated apparently later than the Trochodendrales. The Cercidiphyllaceae diverged earlier in this group, which implies that this family and the Trochodendrales form a primitive group in the subclass. The Cercidiphyllaceae is either placed in Hamamelidales (Cronquist 1981, Thorne 1983), or treated as an independent order (Takhtajan 1987).This analysis suggests that the Cercidiphyllaceae is a relatively isolated taxon, far from the Hamamelidaceae but close to the Trochodendrales in relation. The Eucommiaceae and Didymelaceae are both isolated families and considered as two distinct orders (Takhtajan 1987, Cronquist 1981, 1988).The Balanopaceae is included in the Fagales (Cronquist 1981, 1988) or Pittosporales (Thorne 1983), or treated as a distinct order Balanopales (Takhtajan 1987 ).Obviously the Balanopaceae and Eucommiaceae are not closely related because of the sole synapomorphy (placentation).In fact these four families are more or less isolated taxa and it is probably more reasonable to treat them as independent orders. Cronquist ( 1981, 1988) places the Eupteleaceae, Platanaceae and Myrothamnaceae in the Hamamelidales, while Takhtajan (1987)puts Hamamelidaceae and Platanaceae into the Hamamelidales and treats the Eupteleaceae and Myrothamnaceae as two independent monofamilial orders. These three families are grouped by more synapomorphies (palmateveined, serrate or lobate leaves, deciduous and anemophilous plants)which may indicate their close phylogenetical affinity. A core group of the Hamamelidae includes ten families, among which the Hamamelidaceae originated earlier than the others, so that it is a relatively primitive family. The Betulaceae, Fagaceae and Myricaceae differentiated later than the Hamamelidaceae. The former two are very closely related, and thus thought to be two neighbouring orders by Takhtajan (1987)or included in the Fagales by Cronquist (1981, 1988)and Thorne (1983). The Myricaceae and Fagaceae are connected in the cladogram by only a single synapomorphy (endosperm absent), and therefore the close relationship does not exist between them. The Buxaceae, Simmondsiaceae and Daphniphyllaceae form an advanced group, in which they are weakly linked with each other by only one synapomorphy (pollen grains＜25μm). The Daphniphyllaceae is closely related to the Simmondsiaceae, but the Buxaceae is rather isolated. The Rhoipteleaceae and Juglandaceae share a number of synapomorphies (axile placentation, endosperm absent, embryo larger, fruit indehiscent) , forming a highly specialized group. The opinion that the Juglandales is composed of the Juglandaceae and Rhoipteleaceae(Cronquist 1981; 1988, Lu et Zhang 1990)is confirmed by this analysis. A contrary point of view, which treated them as two distinct orders by Takhtajan (1987), apparently could not be accepted. The Casuarinaceae was regarded as the primitive angiosperm (Engler 1893), but in fact it is a highly reduced and specialized group. It is united with Rhoipteleaceae and Juglandaceae by four synapomorphies, i. e. placentation type, endosperm absent, embryo large and fruit indehiscent. However, the family presents six autapomorphies, and thus the position of the Casuarinaceae as an advanced family is confirmed by this analysis. Finally a strict consensus tree, which represents the phylogenetic relationships of thefamilies in the Hamamelidae, was given as a result of the analysis.

Pollen grains of 6 genera, including 36 species, of the Betulaceae, were examined under LM, SEM and TEM.Their morphological characters are described and three types of pollen are distinguished here. The evidence from pollen morphological characters does not support Hutchinson's (1973)and Dahlgren's (1983)treatments which divided the Betulaceae into two families: Corylaceae ( including Corylus, Ostryopsis, Carpinus and Ostrya) and Betulaceae (including Alnus and Betula). The author agrees with Abbe's (1974)division of the Betulaceae into three tribes with one modification that Ostryopsis is transferred from the tribe Coryleae to the tribe Carpineae. The limits of the three tribes presented here are the same as Kuprianova's (1963) treatment in which she divided the Betulaceae into three families. It is more reasonable to treat Kuprianova's families as tribes. Pollen morphological characters of the three tribes of the Betulaceae are described as follows: 1. Tribe Betuleae (including Alnus and Betula): Pollen grains are triporate or stephanoporate and oblate, suboblate or spheroidal. Sometimes the exine has arci and the ektexine thickens in the apertural region; the sculpture of exine is slightly rugulate under scanning electron microscope (SEM) ; the exine structure is four-layered: tectum, columellae, footlayer and endexine. The columellae are columellate, the endexine thickens in the apertural region and sometimes it is separated from the footlayer to form vestibulum. 2. Tribe Coryleae (only Corylus): Pollen grains are triporate and suboblate. The exine has no arci and the ektexine does not thicken in the apertural region; the sculpture of exine is slightly rugulate under SEM; the exine structure is five-layered: granular layer, tectum, columellae, footlayer and endexine. The tectum is vovered with a granular layer, the columellae granular and the endexine thickens but is not separated from the footlayer in the apertural region. 3. Tribe Carpineae (including Ostryopsis, Carpinus and Ostrya): Pollen grains are mostly triporate and suboblate. The exine has no arci and the ektexine does not thicken in the apertural region; the sculpture of exine is slightly rugulate under SEM; the exine structure is five-layered which is the same as those of the Coryleae. The tectum is covered with a granular layer, the columellae are columellate and the endexine is neither thickened nor separated from the footlayer in the apertural region. The operculum exists on the top of aperturemembrane.

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The flower develops in March and blossoms in early May in Nanjing. The cytokinesis of microsporocytes is simultaneous and most tetrads are tetrahedral. The tapetum is secretory and the nuclei become polyploid at last. The style is solid and most ovaries are unilocular, rarely bilocular. The ovule is pendulous, anatropous and unitegmic. The nucellus is pseudocrassinucellate. An obturator formed by transmitting tissue covers the micropyle. The raphe vascular strand extends into the integument when it reaches the chalaza and on a whole keeps a “U” shape. The endothelium cell is uninucleate. In most cases no nucellar cap is formed. No hypostase is found below the embryo sac. The archesporium is one-celled. The embryo sac development conforms to the Polygonum or Allium types. The degeneration of the megaspores in the linear tetrad usually occurs from the chalazal toward the micropylar end. Two synergids persist during fertilization. Three antipodal cells are uninucleate and ephemeral. Two polar nuclei fuse at the time of fertilization. The fertilization type accords with porogamy. The syngamy is premitotic. The development of endosperm is cellular. The initial four successive divisions of the primary endosperm cell are transverse-verticaltransverse-transverse subsequently, giving rise to sixteen cells of the early endosperm. The mature embryo is straight and nearly as long as the endospermous seed. The cotyledons are more or less cordate at base. The seedoat is thin and composed of 5-11 layers of compressed cells. Neither embryo nor endosperm contain the alkaloid camptothecine. The major similarities of Nyssa sinensis to the American nyssas in embryology, which may be a counted as the generic features, are the polyploid tapetum cells, the unitegmic ovule with U-shaped vascular strand, the direct enlargement of the archesporial cell to produce the megasporocyte, the pseudocrassinucellus, the usual absence of the nucellar cap, the Polygonum or Allium type of the embryo sac development, the first degeneration of the metachalazal megaspore, the ephemeral antipodal cells, a single nucleolus in the nucleus ofthe primary endosperm cell, the more or less cordate base of the cotyledons.

The present paper is a report on combined cytological and taxonomical studies of Polygonatum odoratum and P. cyrtonema. Based on the extensive field observation and mass collection for some years, the authors made a detailed comparison of the variation pattern of morphology、cytology as well as geographic distribution between forms of P. odoratum and P. cyrtonema. The results show that: Form I: Stem angular, leaves elliptic, peduncles with one, rarely two flowers, perianth 1.7-2.0 cm long, stamens adnate to perianth in the middle part or a little lower. The karyotype formula is 2n=20=12m+8sm (2SAT); Form II: Stem angular, leaves narrow-oblong, peduncles with 2-3 flowers, perianth 2.8-3.2 cm long, the position of stamens on perianth is above the middle part. It has the karyotype 2n=20=8m+1osm(4SAT)+2st; Form III: Stem terete, leaves oblong-lanceolate, peduncles with 3- 10 flowers, perianth 1.5- 2.0cmlong, stamens are adnate to perianth also above the middle part. In this form, two kinds of karyotypes are found: 2n = 22 = 6m+8sm+8st and 2n = 20 = 4m+6sm (2SAT) +10st; Form IV: Stem terete, leaves elliptic, peduncles with 1-4 flowers, perianth 2.3-2.8 cmlong, stamens adnate to perianth above the middle part. The karyotype formulae are 2n = 20 = 4m+14sm (2SAT)+2st and 2n = 20 = 10m+10sm (2SAT); Form V: Stem terete, leaves oblong-lanceolate, peduncles with 3-5 flowers, perianth less than 2.0cm long, stamens adnate to perianth above the middle part. It is of the karyotype 2n=22=4m+8sm(2SAT) +10st. It is pointed out that the P. odoratum collected from the Qinling Range may be a hybrid or an intermediate in the evolutionary process from P. odoratum to P. cyrtonema. The differences between the different forms of P. cyrtonema are obvious and stable, and are probably derived from the chromosomal variation. The different forms of P. cyrtonema may have evolvedfrom P. odoratum along different courses.

The genus Acidosasa was published by the present authors in 1979. It only had one species at that time, Acidosasa chinensis C. D. Chu et C. S. Chao. Since then species number of the genus steadily increases. The authors have rather comprehensively studied this genus and its related genera for F1. Reip. Pop. Sin. The present paper deals mainly with morphological characteristics of the genus Acidosasa and the differences from its related genera i. e. Arundinaria, Sasa and Indosasa. The genus Acidosasa is closely related to the genus Arundinaria in the type and origin of inflorescences and the vegetative appearance. But it differs from Arundinaria in the structure of florets. In Acidosasa, each floret is provided with six stamens, while in Arundinaria each floret is of only three stamens. The genus Acidosasa is similar to the genera Indosasa and Sasa in the numbers of stamens, but it is distinguished from lndosasa by its semelauctant (determinate) inflorescence, not iterautant (indeterminate) one, from Sasa by its taller stature and branch complement with three branches. We have carefully examined all the type specimens of Acidosasa and its related genera. A conclusion reached is that there are six species in the genus Acidosasa, most of which are native to S. China, with only one species in Viet Nam. Five specific binomials are reduced and one species is transferred into this genus. Two keys to species, respectively based on the flowering and vegetative characters, are given as follow: Key to species of the genus A cidosasa (1)(based on the flowering state) 1. Lemmas glabrous. 2. Spikelets stout, 3-6mm broad, pedicels 1.5-4cm long; lemmas large, 1.5-2.2cm long, with 15-19 nerves, subcoriaceous, not glaucous, shiny. 3. Lemmas up to 2.2cm long with conspicuously transverse veinlets, tessellate; palea and rhachilla entirely. glabrous, lodicules elliptic-lanceolate, glabrous ... 1. A. chinensis 3. Lemmas 1.5-1.8cm. long, slightly tessellate; palea puberulous at apex of carina, rhachilla puberuous at apex, lodicules obovate, ciliate at apex ............ 2. A. brilletii 2. Spikelets rather slende, 2-4mm broad, pedicels 0.5-1cm long; lemmas small, about 1.3 cm long, with 7-13 nerves, more or less glaucous .......... 3. A. chienouensis 1. Lemmas pubescent. 4. Glumas and lemmas densely pubescent ........................ 4. A. hirtiflora 4. Glumas subglabrous, lemmas sparsely pubescent. 5. Spikelets large, 3-7 cm long, lemmas 1.6-1.7 cm long, pedicels 2-13 mm long ................................................. 5. A. longiligula 5. Spikelets small, 2-3.7 cm long, lemmas about 1.3 cm long, pedicels 1-3 cm long ................................................... 6. A. venusta Key to species of the genus A cidosasa (2) (based on the vegetative state) 1. Ligules of leaf-sheaths strongly elevated, usually 2-8 mm long. 2. Young culms with bristly sheath scars; culm-sheaths without auricles and oral setae, not spotted, sheath-blades erect ................. 4. A. hirtiflora 2. Young culms with glabrous sheath scars; culm-sheaths with small auricles and oral setae, sparsely spotted, sheath-blades reflexed .......... 5. A. longiligula 1. Ligules of leaf-sheaths inconspicuous, less than 2 mm long. 3. Young culms more or less bristly, or sheath-scars bristly: 4. Culm-sheaths without auricles and oral setae, not farinose, without hairs at base. 5. Young culms densely bristly; culm-sheaths attenuate at apex and as wide as sheath-blades, with conspicuously transverse veinlets; leaf-blades large, usually 2.5-3.5 (-6.5) cm broad, conspicuously tessellate ..................................................... 1. A. chinensis 5. Young culms sparsely bristly; culm-sheaths truncate at apex and broader than sheath-blades, without transverse veinlets or inconspicuous; leaf-blades small, 1.5-2.5 cm broad, without visible transverse veinlets .................................................... 6. A. venusta 4. Culm-sheaths with auricles and oral setae, slightly farinose, densely bristle at base; leaf-blades rather narrow, 0.8-1.8 cm broad ............ 3. A. chienouensis 3. Young culms entirely glabrous; leaf-blades rather narrow, 1.2-1.8 cm broad ....................................................................................... 2. A. brilletill