| Celastrus L. (Celastraceae) contains about 30 species which is distributed in Asia, Oceania, South and North America and Madagascar. China is one of the diversity centers of the genus, which is recorded as 24 species in Flora Reipublicae Popidaris Sinicae (FRPS) (vol.45) and 25 in Flora of China (vol.11). Though widely distributed, it is complicated in morphological variation, and the subgeneric classification and taxonomic of some species are still not well resolved. Many systematic studies are still empty or poorly studied and several problems are left. Hence, it is necessary to take comprehensive systematic studies and to perform the taxonomic revision.In the morphological study, more than 6500 herbarium specimen were observed, more than 50 filed populations were investigated and nearly 1200 sheets of specimen were collected with the pursers of clarify morphological variation scale and pattern, and its value in taxonomy. The result shows that seed morphology plays an important role in species identification. First, three types in Celastrus L. can be found based on seed number per fruit and its shape:1) 1-seeded type, whose seed is more than 6 mm in length, including C. hindsii, C.monospermus, C. monospermoides and C. virens; 2) lunate seed type, which is 3--6-seeded per fruit that is short than 5 mm in length, including C. aculeatus. C. kusanoi, C. stylosus, C. hirsutus and C. yuloensis; 3) elliptic seed type, which is 3--6-seeded per fruit, including all the remaining species. Second, articulation position on stalk is also found to be important in taxonomy, which can be divided into upper, in the middle and lower types. Third, pubescence, lenticel and the color above and beneath the articulation on stalk are also valuable in species identification of Celastrus L. Furthermore, calyx when fruited, color of branch, volume and density of lenticel, shape and volume of axillary bud are valuable in species taxonomy in the genus.Micromorphology of leaf, pollen and seed coat of Celastrus L. were comprehensively investigated in this study. Micromorphology of leaves in 14 species were observed under scanning electron microscope (SEM), the result shows that stomas only exist on beneath leaves, and most of them are elliptic, length/width varies between 1.10—1.67, stoma density 188—464/mm2. Inner margin of the outer rim in stoma is smooth, wave-like or erose, the protuberance around per stoma exists in most species. The result also shows that pubescence density on leaf is not stable, which is less valuable in taxonomy. It is the first time that cork-warts in C. hindsii are found, which provides clues in understanding the relationship among species distributed in tropics and temperate. Micromorphology of leaf in Glyptopetalum Thw. and Bhesa Buch.-Ham. ex Am. were also examined. The result indicates that micromorphological characteristic of Bhesa rohusta is obviously different from the others, which supports the treatment to exclude the genus out of Celastraceae. Pollen morphology of 6 species in Celastrus L. were observed and the result shows that pollens are sub-globes, belonging to the typical tricolporate type, the outlayer is reticulate, the diameter 20—25μm. The morphology of pollen intra and inter genus Celastrus are basically the same, which plays little role in taxonomy. Seed coat of 15 species were examined and the result shows that distinct differences exist among species. Seed coat of most species are reticulate, part of them are slightly rugose; seed coat of most species are glabrous, part of them are punctiform; the rim distinct or not. Though morphological differences of seed shape and testa are obvious among species, it do not support the existing subgeneric, series and sectional classification. Seed coat of Tripterygium wilfordii Hook. f. was also observed and the result demonstrates that it is clearly different from that of Celastrus L.By sample of 52 samples representing 28 taxa, and two nuclear (ITS and ETS) and three plastid (psbA-trnH, rpl16 and trnL-F) markers were employed, it was the first time to use most parsimony method and Mrbayes method for comprehensive molecular phylogenetic study of Celastrus L. The result shows that Celastrus may not be a natural monophyletic group and its relationship with Tripterygium need further investigation. The genus Celastrus is composed of one basal.clade and one core group that is composed of six subclades with high support values. The result refuses the traditional subgeneric classification based on sexuality, distribution pattern and inflorescence type. However, seed shape is indicated to be more valuable in subgeneric classification. Furthermore, species relationships are more related in latitude than continental distribution pattern.Based on literature reading, specimen examination, field population investigation, and systematic researches including morphological and molecular phylogenetic studies, three sections are proposed: sect. Sempervirentes (Maxim.) C. Y. Cheng & T. C. Kao, sect. Laterales (W. C. Die) X. Y. Mu & Z. X. Zhang sect, nov., and sect. Celastrus.20 species in China are finally identified and described. Among them, two new species, C. obovatifolius X. Y. Mu & Z. X. Zhang and C. yuloensis X. Y. Mu are found; one species, C. monospermoid.es Loes., is found as a new record in China; five taxa, C. glaucophyllns Rehd.& Wils., C. homaliifolius Hus, C. hypoleucoides P. L. Chiu, C. rosthornianus Loes. var. loeseneri (Rehd.& Wils.) C. Y. Wu and C. stylosus Wall. var. puberulus (Hsu) C. Y. Cheng& T. C. Kao are treated as synonyms of C. hookeri Prain, C. stylosus Wall., C. hypoleucus (Oliv.) Warb. ex. Loes., C. rosthornianus Loes. and C. stylosus Wall., respectively. The legal taxonomic name of Celastrus benthamii (Gardn.& Champ.) is qualified instead of C. monospermus Roxb. One taxon is left because of lacking material.
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