Abstract: Vegetative hybridization between Sea Island cotton (G. barbadense L.) and Upland cotton (G. hirsutum L.) has been carried out since 1950. Varieties of the two species used in this investigation were: G. barbadense L. Sea Island cotton Wenghan perennial cotton Lianher perennial cotton Shihping perennial cotton Lhaderfuejin G. hirsutum L. D.P.L. 14 Delfose 531 Combodia Lihsien 72 Inarching and cleft-grafting were employed. Both stock arid scion were used as mentors in order to obtain desirable influence. This investigation has led to the following conclusions: 1. Inarching was the simplest grafting operation. It assured over 90% of successful union. Cleft-grafting, when skilfully performed, gave 70% stand. 2. When inarching was employed, adventitious roots developed after the cut surface was immersed into water. It was suggested that this might be used toadvantage in rapid propagation of valuable materials. 3. Special attention must be paid to enviromental conditions and to making adjustments of the number of leaves for the purpose of getting desirable effect of the mentor. 4. When properly grafted and trained by the method of vegetative hybridization, variations in physiological characters of the Sea Island cotton could be detected during the growing season. The grafted plants came into flower one month earlier than control. 5. It was interesting to note that the character of early flowering became even more apparent in the second and the third generations; some plantes came into flower two months earlier, these indicating that this character has been altered and inherited. Wide varieability with regarded to the degree of the earliness was also observed. 6. After grafting for two times, the improvement on earliness of the Sea Island cotton seemed to have been strengthened and stabilized. 7: Instances of the mentor influence, such as: (1) the first fruiting branch appearing from the 5th to the 14th nodes, (2) the length of fiber varying from 30.25 to 47.00 mm, (3) the height of plant varying from 93 to 217 cm, (4) the length of the first node of fruiting branch varying from 4 to 20 cm etc., could be readily examined and lead us to understand that alteration and segregation of characters did occur in the progenies of vegetative hybrids. 8. These conclusive evidences gave us an increased understanding on the essence of heredity and proved concretely that the theories developed by Mendelian-Morganian geneticists did not stand criticism. In Nanking, it was difficult to obtain mature seeds of Sea Island cotton under ordinary growing conditions. Plants had to be transferred into a greenhouse to mature. But progenies of vegetative hybrids proved that the production of Sea Island cotton, which was of warm climate origin, could be extended to further north temperature regions.