| The experiment was conducted by crossing four variations of Rosa multiflora (R..multiflora 'inermis No.3', 'inermis No.4', 'inermis No.ll' and R.mutiflora Thunb.f.carnea ) and analyzing their cross-compatibility and character segregations among their offspring in order to select the best cross combinations that are able to produce excellent seedlings of rose rootstock and helpful for further researches in this project. Meanwhile, laws on seedling crown formation and ways of controlling its elongation have been studied so as to make better use of seedling rootstock . The experiment results are presented as follows:1.Althought character segregations were obvious among hybrids, which showed great potential on further selections. Offspring, which are uniform , strong and suitable to produce seedling rootstock , were produced from the combinations of No.3×No.4,No.4×No.3 and No. 11×No.3.2.From exteral appearance, the root crown develops from the Hypocotyl, while anatomically, it is consist of the Cotyledon Node Zone and Hypocotyl .The convertion of primary vascular system occurs in the Cotyledon Node Zone between root and stem.3.While shading is useful for the elongation of root crown, its diameter is likely to reduce, which brings negative effects on the later stage of seedling growth. Therefore it is suggested that the length of root crown should be controlled in the range of 2.5 to 3.5cm in order to meet the need of grafting.4.The distribution of crown length is mainly affected by the uniformity of seed germination, the amount of shading time and intensity, The idea rootstock with long root crown are most likely to be available under the conditions of 14 days overshadowe at the light intensity of (4.62±1.1) u mol/( m2.S), after seed sorting by salt water and acid treatment by strong HCL and etc.
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