| Magnolia subgenus Yulania, a deciduous tree found in temperate zones, is an important taxonomic group of Magnoliaceae. There are in subgenus Yulania twenty species, of which one grows in southeast America, three in Japan, and most, however, in China widely cultivated in gardens and used as Chinese medicine for about 2,500 years. Magolia amoena, M.cylindrica, M.zenii, M.campbellii, M.sargentiana and M.dawsoniana are categorized as rare and endangered species under protection now in China.Dandy divided subgenus Yulania into three sections: sections Yulania, Buergeria, and Tulipastrum. This division was done mainly on the basis of the three accepted morphological characters: sepaloid or petaloid tepals, the flowering after or before leaf emergence, and the color of tepals. Seventeen species were tested for RAPD analysis. The results indicated that M.acuminata originating from North America could be obviously distinguished from the other species from Asia in the cluster analysis. This consisted with the result of cpDNA sequence analysis. There was a slight difference between the former two ways in the taxonomic position of several species, such as M.campbellii and M.zenii. It might be a difference in the accurate rate of the two ways. The results from RAPD and sequence analysis did not support sectional treatments of the subgenus Yulania based on sepaloid tepals, time of flowering, and the tepal color. It was suggested that subgenus Yulania could be divided into two sections: section Yulania (Spach) Y.L.Wang,sect. nov. and section Tulipastrum(Spacti) Y.L.Wang, sect. nov..Being a taxon of wide distribution and easy hybridization, subgenus Yulania produces various species which include about 14 natural species and near 20 cultivated breeding reported in China. And they have not been studied taxonomically. As an attempt to study the taxonomy in cultivated species level of Magnoliaceae, 20 various species were tested for RAPD analysis.Based on the RAPD analysis and some morphological characters, the materials of Yulania were divided into five groups: Yulania, Liliflore, Biondii, Sprengeri, and Soulangeana group.The results also implied that RAPD patterns within subgenus Yulania were highly polymorphic. They could be effectively applied to the classification of Magnoliaceae atthe lower taxonomical unit. Two hundred and seventy-four sites were detected by 15 10-mer primers, out of which 262 were polymorphic (95.6% of the total loci detected). All of the materials were clearly distinguished, of which fourteen samples have forty-five typical RAPD bands.Before the molecular taxonomy was introduced, people never doubted subgenus Yulania's disrelation with subgenus Magnolia and a close relation between subgenus Yulania and Michelia, as there is in both genera a sameness seen in their prolepsis and powder chambers dehiscing on the side. In this study of the author, a cross of Magnolia liliflora and Magnolia 'hongyuanbao' with Michelia foveolata and Michelia yunnanensis produced a high fruit rate of about 81-100 percent. These hybrids were highly vigourous. This suggested a second time that there existed a very close relationship between the two. This inspired a further study of the species, i.e. a search for the proof in chromosome data.After a discussion about the various morphological characters and the mechanism of flowering based on the years' observations and study on the specimen, the author presents in the end a clear result that the shape of tepals, the position of flower buds and the flowering time are varied in a certain scope.
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