The “lower” Hamamelidae sensu Endress (1989a) comprises seven families: Trochodendraceae, Tetracentraceae, Cercidiphyllaceae, Myrothamnaceae, Eupteleaceae, Platanaceae and Hamamelidaceae. In the present paper, the systematic position, modern distribution pattern and fossil history of each family are analyzed, and the origin and dispersal of them are discussed according to the principle of the unity between the phylogeny and distribution of plants. The paper consists of three parts. The conclusions are as follows: 1. The center of distribution According to Takhtajan's (1986) regionalization of the world flora, there are 13 distribution types in the “lower” Hamamelidae (Table 1 ). Eastern Asiatic Region, with five families, 19 genera and 73 species, ranks the first based on the numbers of species, genera and families. Four families: Trochodendraceae, Tetracentraceae, Cercidiphyllaceae and Eupteleaceae which were considered as more primitive in the “lower” Hamamelidae and three genera: Disanthus, Exbucklandia and Rhodoleia, primitive in the Hamamelidaceae, are all found in Eastern Asiatic Region. In addition, the groups at different evolutionary stages in the “lower” Hamamelidae survive in this region. Indochinese Region, with two families, 15 genera and 32 species, ranks the second. It was shown that southern Eastern Asiatic region and northern Indochinese Region are the distribution center of the “lower”Hamamelidae based on further analysis (see Table 2). 2. The place and time of the origin The fossil records of the “lower” Hamamelidae are abundant in angiosperms. Nordenskioldia, supposed as the extinct ancestral group of Trochodendraceae and Tetracentraceae, was widely distributed during the latest Cretaceous and the early Tertiary in the Northern Hemisphere; Trochodendroides appeared during the Cretaceous in North America, former USSR and Japan; the ancestral group of Cercidiphyllaceae, the Joffrea-Nyssidum complex, also occurred during the Cretaceous in the middle and higher latitude area of the Norhern Hemisphere. In addition, the earliest fossil records of the Eupteleaceae, Platanaceae and Hamamelidaceae appeared in North America, Europe and Asia of the Northern Hemisphere respectively. Therefore, the Laurasian origin of the “lower” Hamamelidae is supported by fossil evidence. On the other hand, the fossil data are still insufficient to determine the place of the origin, especially because the fossil records are rather poor in Asia. For this reason, the analyses of birthplace should combine with the information from the distribution of the primitive groups or outgroup of the “lower” Hamamelidae. Based on the statistics of distribution types, there are four primitive families in the “lower” Hamamelidae and three primitive genera in the Hamamelidaceae in southern Eastern Asiatic Region and northern Indochinese Region. Platanus kerrii Gagnep. of the Platanaceae, distributed in northern Vietnam, is considered as one of the most primitive species which has survived in modern times in this family because of its pistillate inflorescence comprising 10-12 heads. The Magnoliaceae was selected as an outgroup in our other paper “A phylogenetic analysis of families in the Hamamelidae” (Lu et al. 1991 ). All its 13 genera and most species occur from East to Southeast Asia, but in North America only three genera are found. Takhtajan (1969) considered that it was plants of the Magnoliaceae that were dispersed from East Asia to North America. Because the primitive groups of the “lower” Hamamelidae and its outgroup almost occur in the same area, their ancestor also appeared most probably in this area according to the principle of common origin. It was inferred that the area from southern Eastern Asiatic Region to northern Indochinese Region is the birthplace of the “lower"” Hamamelidae. The differentiation of the “lower” Hamamelidae took place rather early in angiosperms. The origin of them may be traced at least back to the Barremian of the early Cretaceous according to pollen fossil records. From more unequivocal fossil evidence, Platanoid plants appeared during the late Albian of the early Cretaceous, and the Trochodendraceae, Tetracentraceae, Cercidiphyllaceae and Hamamelidaceae diverged from their ancestral groups respectively no later than the late Cretaceous (Fig. 6). 3. The causes for the formation of the modern distribution pattern The “lower” Hamamelidae is a. rather old group. It is one of the most abundant and widespread components of fossil floras in the Northern Hemisphere during the late Cretaceous-middle Tertiary, the interval, when the global temperature was warm, although the extant Trochodendraceae, Tetracentraceae, Cercidiphyllaceae and Eupteleaceae which are now confined to East Asia are monotypical or oligotypical families. This distribution pattern indicates that most plants became extinct in Europe, northern Asia and North America because of the climatic changes during the late Tertiary, and especially the Quaternary glaciation, but East Asia, usually called “plant refuge”during the glacial period, became the survival place of many plants. From the viewpoint of evolution, these four families might be “living fossil plants” preserved from the Tertiary. The distribution of Hamamelidaceae is disjunct, but the causes leading to this pattern are not the same in different genera. The disjunction among Europe, North America, Australia and southern Africa is due to the tectonic movements of the earth; , and that between southeastern Europe-northern West Asia and southeastern Asia is developed as a result of the Quaternary glaciation. Fothergilla found from Carolina to Alabama in the United States and Hamamelis disjunct between East Asia and North America were widely distributed during the Tertiary in the Northern Hemisphere (Hu & Chaney 1940). The formation of their distribution patterns is a synthetic process owing to the tectonic movements and the Quaternary glaciation. Parrotia and Parrotiopsis, endemic to Iran and the West Himalayas respectively, are very similar in morphology. They might have a common ancestor, and the latter is more primitive than the former. It seems that several groups in the Hamamelidaceae were dispersed from east to west in Eurasia. Of the five genera in the Southern Hemisphere, Dicoryphe and Trichocladus are Madagascarian and southern African, and Ostrearia, Neostrearia and Noahdendron occur in northeastern Australia. They are usually considered as rather isolated groups, but Hufford and Endress (1989) found that they are closely related. The African genera might be dispersed from Asia via India, Sri Lanka and Lemuria continent; the Australian Hamamelidaceae also from Asia, but via the islands distributed in the Pacific Ocean. The Myrothamnaceae, comprising 2 species distributed in Madagascar and southern Africa, is closely related to the Hamamelidaceae. Based on morphological analyses, an evolutionary series exists among Myrothamnus, Dicoryphe and Trichocladus in which the distribution patterns are the same, and Myrothamnus is more specialized than the two genera of the Hamamelidaceae. Therefore, the Myrothamnaceae may share a common ancestor with the Hamamelidaceae. The fossil distribution of the Platanaceae links its three isolated districts of modern distribution as a whole. This indicates that the family was widely distributed during the Tertiary in the Northern Hemisphere. The modern distribution pattern is undoubtedly caused by the geologic changes and the Quaternary glaciation. Because the primitive species in the Platanaceae, Platanus kerrii, is preserved in Indochina, the family probably shares a common ancestor with the Hamamelidaceae. Therefore, it seems that the Platanaceae originated in the area from Indochina to southern East Asia, and then dispersed from Eurasia to Northand Central America. Decontaminated thianthrene disproportion. Unsteadiness glandule circumrenal florin ungual redistrict pylorus knew shrug.
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The three types and eight subtypes of seedlings are recognized in the gymnosperms in the present paper. They are: 1. The Cycas Type: cotyledons 2, with absorptive function, absorbing nutrients from the endosperm (gametophyte); hypogeal; including three subtypes: (1) The Cycas Subtype: internodes not elongated; leaves simple, pinnate; (2) The Ginkgo Subtype: internodes elongated; leaves fan-shaped; (3) The Araucaria Subtype: internodes elongated; leaves linear. 2. The Pinus Type: cotyledons 2 to numberous, with both absorptive and photosynthetic Functions; epigeal; including three subtypes: (1) The Cunninghamia Subtype: cotyledons 2- 4; internodes elongated; leaves linear; (2) The Pinus Subtype: cotyledons numerous; internodes not elongated; leaves needle-like (3) The Ephedra Subtype: cotyledons 2; internodes elongated; leaves scaly. 3. The Gnetum Type: with an absorptive function foot at the base of the hypocotyl, absorbing nutrients from the endosperm; cotyledons 2, with photosynthetic function, epigeal, containing two subtypes: (1) The Gnetum Subtype: cotyledons similar to foliar leaves, like the pinninerved leaves of the Dicotyledons; internodes elongated; (2) The Welwitschia Subtype: cotyledons linear, internodes absent, the whole plant with only a pair of leaves. Detailed descriptions and a key to the three types and eight subtypes are presented in the paper. It is considered that the origin of the gymnosperms is not monophyletic but polyphyletic. That is to say, the seed of gymnosperm is polyphyletic as a result of parallel evolution in different groups of the progymnosperms. According to the morphological characters of the seedling types we propose that there have existed four evolutionary lines in the gymnosperms, namely: the Cycas line, the Ginkgo line, the Conifer line and the Gnetum line, and the evolutionary process of each line is explained. The evolutionary relationships among the three types and eight subtypes are discussed. There is a foot in the Gnetum Type, which is uncomparable with any seedling type of seed plants, since it has its unique developed line and differentiated into the Gnetum Subtype and the Welwitschia Subtype. The evolutionary tendency is from hypogeal to epigeal in the other types and subtypes. Cycas and Ginkgo are relict with seedling types belonging to the Cycas Subtype and the Ginkgo Subtype respectively, which have maintained an ancient character-hypogeal. Therefore, the evolution of seedling types is from the Araucaria Subtype to the Pinus Type, and the latter itself differentiated into three subtypes. Moreover, it is explained why there are stomata on the hypogeal cotyledons of Cycas and Ginkgo when the footed embryo of the progymnosperms changed to the embryo of the Cycas type via neoteny, the foot was lost, and the first two leaves on the stem tip were arrested, changing to the cotyledons of the Cycas Type and replacing the foot of the progymnosperms as an absorptive organ. The stomata on the cotyledon epidermisof Cycas and Ginkgo are a residue of the first two leaves of the progymnosperms.

Seeds of 201 species of 83 genera in the Gramineae were collected from the tropical and subtropical regions of Australia, and the temperate region of China. Pure live seeds of each species were sown in plastic pots, which were filled with the mixture of sand and bits of rotted wood (4:1). Seeded pots were kept in greenhouse at temperature of 20—25°C , and were arranged at random with four replications in each of the two treatments of sowing depth, 10 mm and 0 mm. The seedlings were taken as samples for examining 60 morphological and microscopic characters (Appendix), when they grew to the three-leaved stage. Cluster analysis was made using 60 seedling characters with the 201 species as OTUs. As a result, four clusters are recognized as follows. Cluster 1. Festucoid: The group consisted of all the species of the subfamily Festucoideae, the species of the genera Stipa, Achnatherum, Danthonia and Aristida in the subfamily Arundinoideae, and those of the genus Microlaena in the subfamily Bambusoideae. The seedling mesocotyl elongated or not, but not elongated when grew under light. Mesocotyl roots absent. Scutellum and coleorhiza node roots or coleoptile node roots dominant. The first leaf narrowly linear, erect, acute at the apex, twisting clockwise or counterclockwise; blade and sheath 3—5-nerved, with the blade length/width ratio 61.65 on an average; The second and third leaves narrowly linear, acute or acuminate at the apex. The coleoptile 13.04mm long on an average. The first tiller appeared when the third leaf emerged. Cluster 2. Panicoid: All the species of the subfamily Panicoideae, the species of the genera Eriachne and Monachather in the subfamily Arundinoideae, and the genus Enneapogon in the subfamily Eragrostidoideae were included in this group. The seedling mesocotyl elongated, even if growing under light. Mesocotyl roots present and dominant. Scutellum and coleorhiza node roots absent. The first leaf oblong-lanceolate, oblong-oblanceolate or spathulate, ascendent or horizontal, acuminate or obtuse at apex, not twisting; blade and sheath over 7-nerved, with the blade length/width ratio 8.95 on an average. The second and third leaves linear-lanceolate, lanceolate or oblong-lanceolate, acuminate at the apex. Coleoptile 5.29mm long on an average. The first tiller appeared when the fifth leaf emerged. Cluster 3. Bambusoideae: This group included the species in the subfamily Bambusoideae except those in the genus Microlaena. The first and second leaves without blade in the supertribe Bambusanae. The mesocotyl not elongated. Scutellum and coleorhiza node roots, and coleoptile node roots completely absent, only primary root developed. The mesocotyl elongated, mesocotyl roots absent and coleoptile roots dominant in the supertribe Oryzanae. The blade of the first leaf suppresed, but the second and third leaves both with blade and sheath. Cluster 4. Eragrostidoid: The cluster contained the species in the subfamily Eragrostidoideae except those in the genus Enneapogon. The seedling mesocotyl elongated, but not elongated when grew under light. The mesocotyl roots mostly absent, while the coleoptile node roots dominant. The first leaf linear, almost ascendent, acute at the apex, not twisting, blade and sheath 5—7 (9)-nerved, with the blade length/width ratio 11.69 on an average. The second and third leaves linear, linear-lanceolate or lanceolate, acuminate at the apex. The coleoptile 2.60 mm long on an average. The first tiller appeared when the fifth leaf emerged. The species of the subfamily Arundinoideae were divided into four clusters. The results showed that the Arundinoideae could be considered as primitive member of the family, from which the subfamilies Panicoideae, Eragrostidoideae and Festucoideae are derived and specialized. With exception of a few cases, species in a genus were generally clustered into one unit and grouped into a subcluster unit. Seedling characters, like other taxonomic characters, are of importanttaxonomic significance, and could be used in classification of the Gramineae.

Ixeris Cass., strinctly speaking, is confined to plants which have achenes with sharply winged ribs. Ixeridium (A. Gray ) Tzvel. contains plants which have persistent radical leaves at anthesis and achenes with obtuse ribs and a fine rostrum at its apex. Paraixeris Nakai is restricted to plants which are of the same achenes as in the genus Ixeridium (A. Gray) Tzvel., but rostra of achenes are robust and radical leaves deciduous in flowering in the former. The Chorisis DC., a monotypic genus, is characterized by ternate palatisect leaves. In the light of the above mentioned understanding of these genera, the author thinks that the division of Chinese Ixeris group, a comparatively complex one, into four genera would be more reasonable than merging them into one genus, namely, Ixeris Cass. Based on the examination of specimens in the Herbarium of the Institute of Botany, Academia Sinica (PE), the author found that there are four species in the genus Ixeris Cass., including one new combination in China. They are I. polycephala Cass., I. dissecta (Makino) Shih, I. japonica (Burm. f. ) Nakai and I. stolonifera A. Gray. The genus Ixeridium (A. Gray ) Tzvel. has 13 species, including five new combinations and three new species in China, namely, I. sagittaroides (C. B. Clarke) Shih, I. gramineum (Ledb.) Tzvel., I. yunnarense Shih,I. graminifolium(Ledb.)Tzvel.,I, biparum Shih,I.aculeolatum Shih,I. chinense( Thunb. ) Tzvel., I. strigosum( Fisch. ) Tzvel., I. elegans( Franeh. ) Shih, I. sonchifolium (Maxim.)Shih,I. laevigatum (BI.)Shih,I. dentatum(Thunb. )Nakai and I. gracile(DC.)Shih, in China. There are six species in the genus Paraixeris Nakai, including One new combination, namely, P. denticulata(Houtt.) Nakai, P. humifusa(Dunn) Shih, P. cheldonifolia( Makino) Nakai, P. saxatilis( Baran. ) Tzvel., P.pinnatipartita (Makino)Tzvel. and P.serotina(Maxim.)Tzvel.in China.

Fifteen species in six genera of the family Liliaceae were karyomorphologically studied. They share the complex chromocenter type of the resting nuclei and the interstitial type of the prophase chromosomes in somatic cells except that Clintonia udensis Trautv. et Mey is of the densely diffuse type and gradient type respectively. Their karyotype formulas are listed as follows: Clintonia udensis Trautv. et Mey, 2n= 14=8m+4sm+2st (2SAT), belongs to 2A type; Smilacina henryi (Baker) Wang et Tang, 2n=36=12m+16sm+6st+2t (2SAT), 2C type; Smilacina fusca Wall., 2n = 36= 14m (2SAT) + 12sm+ 10st(2SAT), 2B type; Smilacinata tsienensis (Franch.) Wang et Tang, 2n= 36=22m +2sm+ 2st(2SAT), 2C type; Smilacina atropurpurea ( Franch.) Wang et Tang, 2n=36=18m+6sm(2SAT) +12st, 2C type: Polygonatum kingianum Coll, et Hesml., 2n=30= 12m(2SAT) +6sm+ lst+2t, 2C type; Polygonatum cirrhifolium (Wall.) Royal, 2n=30= 10m+4sm+ 12st+4t, 3C type; Polygonatum curvistylum Hua, 2n=78=24m (2SAT)+ 14sm (6SAT)+40st, 3C type; Polygonatum cathcartii Baker, 2n = 32 = 12m + 6sm + 10st+ 2t + 2Bs, 2C type; Lilium henricii Franch., 2n = 24 = 2m(2SAT) + 2sm + 10st+ 10t, 3A type; Lilium bakerianum Coll. et Hesml. var. rubrum Stearn, 2n=24=4m ( 2SAT) +10st+ 10t (2SAT), 3A type; Nomocharis bilouensis Liang, 2n= 24= 2m (2SAT) +2sm+ 12st+ 8t, 3A type; Nomocharis pardanthina Franch., 2n= 24=4m (2SAT)+12st (2SAT)+ 8t, 3A type; Nomocharis sauluensis Balf. f., 2n=24=4m(2SAT) +10st (2SAT) + 10t, 3B type; Notholirion campanulatum Cotton et Stearn 2n = 24 = 2m (2SAT) + 2sm + 14st(2SAT ) + 6t, 3A type.

The karyotypes of 3 species of Roegneria and 2 species of Kengyilia were analysed in this paper. They are all reported for the first time, and the karyotype formulae are as follows: R. nutans, 2n = 4X= 28 = 26m+ 2sm; R. abolinii, 2n = 4X =28 = 24m + 4sm; R. aristiglumis, 2n = 6X = 42 = 32m + 10sm (2sat); K. tahelacana 2n = 6X = 42 = 36m (2sat)+6sm (2sat); K. zhoasuensis, 2n = 6X= 42 = 34m(4sat)+ 8sm. According to the characters of karyotypes, K. tahelacana and K. zhoasuensis havethe S, Y, P genomes of genus Kengyilia.

Gypsophila huashanensis Y. W. Tsui et D. Q. Lu and G. spinosa D. Q. Lu (Caryophyllaceae) are described as new from China.

Thirteen new species of pteridophytes are described from the Hengduan Mountains, China. They are Selaginella laxistrobila Shing, S. trichophylla Shing, Hypodematium daochengense Shing, Stegnogramma latipinna Ching, Pseudocyclosorus pseudorepens Ching et Y. X. Lin, P. subfalcilobus Ching, Pyrrosia pseudodrakeana Shing, Lepisorus neolewisii Shing, L. bilouensis Ching et Y. X. Lin, Polypodium muliense Ching, P. nervopilosum Shing, P. intermediumChing et S. K. Wu and P. daochengense Ching et S. K. Wu.

Reported in the present paper are two new species and one new record of Spirogyra. The two new species are Spirogyra subferruginea and S.kweichowensis; the new record for China is Spirogyra brunea Czurda.

The paper presented here is Concerned with the numerical cladisties. In consideration of the fact that the parallel evolution has close relation to the length of evolution graph, a new method of reconstructing evolutionary tree has been developed for the application and practice of cladistics. The procedure of the algorithm of the new method presented in Table I is similar to the method described in paper "An algorithm for cladistics method of maximal same step length". An essential step of the algorithm is how to decide the coefficient between two cladistic units (CTUs). A coefficient called parallel evolutionary coefficient between CTUp and CTUq is defined as follows: where the j is code of CTU and the i is code of character; E(p, q, i, j) is a function given by following expression: min (X_ij, Xpj)+(X_ij, Xqj)-2min(Xpj, Xqj) as Xij>min (Xpj, Xqj) E(p,q, i,j ) = 0 otherwise. where the X_ij is the ith row (CTU) jth colunm (Character) element of the data matrix. Because the method of minimal parallel evolution is closely related to the length of evolutionary graph, it is superior to the method of maximal same step length. A simple datum as an example for comparison shows that the method of minimal parallel evolution can arrive at a better result. But in some cases, we may combine one method with another and thus the coefficient should take following form: S(S_ij)=M·S (C) _ij-N·S(P) _ij in which S (C) _ij and S (P) _ij are the same step coefficients and the parallel evolution coefficient respectively, and the M and N are positive integers as a weightnumber being given in advance.