Table of Contents

10 July 1997, Volume 35 Issue 4
    Research Articles
  • Wang Qing-feng, Chen Jia-kuan
    J Syst Evol. 1997, 35(4): 289-292.
    The floral organogenesis of Caldesia parnassifolia (Bassi ex L. ) ParI. was observed under scanning electron microscope (SEM). The primordia of the floral appendage initiated in trimerous pattern and acropetal succession. Three sepal primordia first initiated on radii spirally, and a whorl of three alternisepalous petal primordia formed nearly simultane ously after the inception of sepal primordia. The petal and stamen primordia initiated separately, and no petal-stamen complex was observed. The three anti-sepalous outer stamens arised after the initiation of petals, the other three inner (anti-petalous) stamens arised subsequently, and the six stamens were arranged in one whorl at subsequent stages of development, but still anti-sepalous and anti-petalous separately. The first whorl of 3 pistil(carpel primordia originated opposite the sepal primordia, while subsequent pistil primordia formed rapidly in alternation with the preceeding ones, each whorl with 1~3 pistils. The significance of the spiral, acropetal development of corolla is discussed.
  • Guo Yan-ping, Pan Kai-yu, Ge Song
    J Syst Evol. 1997, 35(4): 293-296.
    Reported in this paper are the microsporogenesis, megasporogenesis and the development of male and female gametophytes of the endangered species Adenophora lobophylla. The anther is four-sporangiate with its wall composed of four layers: epidermis, fibrous endothelium, middle layer and glandular tapetum of binucleate cells. The cytokinesis of microspore mother cell in meiosis is simultaneous, and tetrads are tetrahedral. Pollen grains are 2-celled at the dispersal stage. Ovule is anatropous, unitegmic and tenuinucellate with a hypodermal archesporial cell developing directly as the megaspore mother cell which undergoes meiotic division and then forms a linear tetrad. The embryo sac is of Polygonum type. The polar nuclei fuse before fertilization. An endothelium differentiates when the uninucleate embryo sac forms. Comparative studies were made with the closely related and widely distributed species A. potaninii. No differences between them were found. No obstacle to sexual reproduction in this endangered species was observed. As a conclusion, no endangering factors were found to influence the sporogenesis and gametogenesis of A. lobophylla. According to our observision and the references on embryological studies of the Campanulaceae(s. l. ), there is no evident differentiation in sporogenesis and gametogenesis in this family.
  • Wang Jian-bo, Chen Jia-kuan, Li Rong-qian
    J Syst Evol. 1997, 35(4): 297-302.
    This paper deals with the embryological characteristics of Sagittaria guayanensis H. B.K. subsp. lappula (D. Don) Bojin. The anther wall development follows the Monocotyledonous type. The cytokinesis of microspore mother cell in meiosis is of the Successive type. The tetrads of microspores show an isobilateral arrangement, and the mature pollen grains are 3-celled. The ovule is bitegminous, pseudo-crassinucellate and anatropous. The megaspore mother cell originates directly from a single archesporial cell. The mature embryo sac consists of 7 cells including 8 nuclei and conforms to the Allium type. The two polar nuclei do not fuse into a secondary nucleus before fertilization. Instead, one sperm fuses with the micropylar end polar nucleus first , and the fertilized polar nucleus then migrates to the chalazal end, where it fuses with the second polar nucleus, forming the primary endosperm nucleus. The embryo development conforms to the Caryophyllad type. The mature embryo is U-shaped and forms the embryonic shoot apex accompanied by two leaves. The endosperm development corresponds to the Helobial type. The primary endosperm nucleus (invariably lying in the chalazal part of the embryo sac) divides and forms two chambers:large micropylar one and small chalazal one. The chalazal endosperm chamber remains binucleate, while, in the micropylar chamber free nuclear divisions occur and then cellnlarization takes place. During the embryo formation the endosperm gradually degrades and can not be found in the mature seed. The subgenus Lophotocarpus is different from the subgenus Sagittaria in some embryological aspects, especially in the structure of mature embryo sac and the double fertilization process.
  • Wang Shi-jun
    J Syst Evol. 1997, 35(4): 303-310.
    The Cordaitaceae was widely distributed throughout the Euramerican Flora and Cathaysian Flora in the Carboniferous and Permian of the Late Paleozoic. It consists of three natural genera: Mesoxylon, Shanxioxylon and Pennsylvanioxylon. All of them can be found in the Cathaysian Flora, While in Euramerican Flora only Mesoxylon and Pennsy lvanioxylon were discovered. The isolated organs of Mesosxylon have been identified as different organ genera: Stem: Mesoxylon Scott et Maslen 1910. leaf: Cordaites Unger 1850. male strobilus: Gothania Hirmer 1933. female strobilus: CordaitanthusFeistmantel 1876. ovule: Mitrospermum Arber 1910. pollen: Sullisaccites Millay et Taylor 1974, Felixipollenites Millay et Tayllor 1974. And those of Pennsylvanioxylon are: Stem: Pennsylvanioxylon Vogenellhner 1965. leaf: Cordaites Unger 1850. male and female strobilus: Cordaitanthus Feistmantel 1876. ovule: Cardiocarpus Brongniart 1881. pollen: Florinites sensu strictu Millay et Taylor 1974. The isolated organs of Shanxioxylon are put into the same genera as those of Pennsylvanioxylon respectively, except for the stem( named as Shanxioxylon Tian et Wang 1987). Since its stem, leaf, male strobilus and ovule are quite different from those of Mesoxylon and Pennsylvanioxylon, Shanxioxylon is considered as the third natural genus of the Cordaitaceae, which is found only in the Cathaysian Flora at present. The stem and reproductive organs of Mesoxylon are rather primitive. Its stem is similar to that of pteridophytes. The stem of Pennsylvanioxylon is rather advanced and quite similar to that of modern conifers, but its reproductive organs are quite primitive. The stem of Shanxioxylon lies between Mesoxylon and Pennsylvaniomylon, but its reproductive organs have advanced characteristics. It is supposed that Shanxioxylon is probably a kind of plant with great evolutionary plasticity, from which more advanced cordaites or even conifers might have been derived. In fact, stems of one species of Shanxioxylon are quite advanced. For example, it is of typical sympodial vasculature with sympodia undulate along the longitudinal direction, the same as that of modern conifers. Shanxioxylon is probably a kind of cordaites which possesses a great evolutionary potential and is a transitional type linking primitive cordaites and some primitive conifers. In the Euramerican Flora, the earliest fossil record of cordaites is probably at Tournaisian stage of the Early Carboniferous. The appearence of cordaites, especialy the anatomical features, in this time is not clear. The only known organ with internal amatomical structures is an ovule Mitrospermum bulbosum Long. It is inferred that the cordaites in this time probably belong to Mesoxylon. At the Westphalian stage, cordaites become common, but mainly Mesoxylon,such as M. sutcliffii, M. hultirame etc., in the Lower Coal Measures, England. Later, M. sp. (cf. M. multirame or M. sutcliffii ) also occurred in early Middle Pennsylvanian, America. Pennsylvanioxylon came to appear in this time. In the Middle Pennsylvanian, cordaites in North America reached its evolutionary peak. In addition to Pennsylvanioxylon, more advanced species of Mesoxylon (i. e. M. thompsonii )appeared. At the Stephanian stage(late Later Carboniferous) cordaites began to decrease. In the Permian, cordaites became rare except a few leaf impressions. An evolutionary line of cordaites in the Euramerican Flora is proposed based on the fossil record of the Late Paleozoic: Progymnosperm→primitive Mesoxylon (such as Mitrospermum bulbosum , Mesoxylon sutcliffii etc. )→more advanced Mesoxylon (such as M. thompsonii )→Pennsylvanioxylon→extinct. The earliest Cathaysian cordaites were living in the age of Early Carboniferous(Visean Stage). They were all impressions of leaves. The earlist anotomically preserved cordaitean fossils are the stem of Mesoxylon sp. in coal balls of the Hongtuwa Formation(early Late Carboniferous in age), Gansu Province. Lately, in coal balls of the Taiyuan Formation(early Early Permian in age), the advanced cordaites, such as Shanxioxylon and Pennsylvanioxylon, appeared. The fossils of cordaites in China are very abundant throughout the whole Permian beds, so it is convenient for us to study the late evolution of cordaites. Based on the available information, there probably existed two evolutionary lines in the Cathaysian Flora cordaites: 1. Progymnosperm→Mesoxylon→Shanxioxylon→Pennsylvanioxylon→extinct. 2. Progymnosperm→Mesoxylon→Shanxioxylon→extinct or evolved into somenew plants(such as early primitive conifers).
  • Xiong Zhi-ting, Chen Sing-chi, Hong De-yuan
    J Syst Evol. 1997, 35(4): 311-316.
    Taxonomic studies of 11 taxa in Hemerocallis from China were conducted using cluster analysis and principal components analysis. The taxa were grouped into four clusters. The Cluster one includs H. citrina, H. lilioasphodelus, H. minor and H. multiflora ; the second cluster H. dumortieri and H. middendorfii ; the third cluster H. plicata, H. forresti and H. nana; and the fourth cluster di-and triploid of H. fulva. Relationships between the taxa within clusters as well as the subdivision of the genus are discussed.
  • Wang Zhong-ren
    J Syst Evol. 1997, 35(4): 317-340.
    About 300 “species” names of Athyrium from China were published. They are preliminarily treated as 117 species with a number of varieties and hybrids. The complete enumeration will be reported in four parts. The present paper is part one, a key to the species.
  • Yu Shun-li, Lin You-xing
    J Syst Evol. 1997, 35(4): 341-347.
    Based on characters, such as scales on rhizomes, paraphyses in sori, leaves, rhizomes and stipes, the genus Lepisorus is divided into 6 sections. They are Sect. Lepisorus, Sect. Pleioomma S. L. Yu, Sect. Sclerophyllon S. L. Yu, Sect. Macrophyllon S. L. Yu, Sect. Pachyphyllon S. L. Yu and Sect. Hymenophyton Ching.
  • Wu Yu-hu
    J Syst Evol. 1997, 35(4): 348-352.
  • Guo Tian-chi, Ye Yin-min
    J Syst Evol. 1997, 35(4): 353-355.
  • Xiang Qiao-ping
    J Syst Evol. 1997, 35(4): 356-359.
  • Wei Yin-xin
    J Syst Evol. 1997, 35(4): 362-374.
    This paper reports one new species, three new varieties and 20 taxa new to China in eight genera of Desmidiales from Dongqian Lake and West Lake in Zhejiang province, China.
  • Chen Zhi-duan, Lu An-ming
    J Syst Evol. 1997, 35(4): 375-384.
    With the advent of some new techniques, the past several years have been a time of fascinating discoveries on the origin and early evolution of angiosperms. Rapidly accumulating data have resulted in notable progress, and this field is becoming an active and exciting branch of botany. The paper, first, reviews the studies on early angiosperm evolution in the last fifty years; then discusses recent advances that have been made since early 1980s from five aspects, i.e., molecular systematics, cladistics, micromorphology of flowers under scanning electron microscopy, molecular genetics of floral development and the Cretaceous fossil flowers and other reproductive structures; finally, several future directions of the field are briefly discussed.