The objective of these studies were to investigate variations on the agronomical and quality characters caused by the shifting of the seeding date. Experiments were carried out during the period of from 1968 to 1970 at Tobacco Experiment Station, Sosa, Korea, using 50 varieties from four different groups of tobaccos; Flue cured, Native, Turkey (Orient), and Burley tobaccos. Each variety was sown at an interval of 15 days from February 1 to April 17. The results are summarized as follow: 1. For all four groups of tobaccos, number of days to blooming decreased linearly between 1st-4th seeding (Apr. 1-Mar. 18) and increased after 5th seeding (Apr. 2) for Burley tobaccos, after 6th seeding (Apr.17) for all the others, showing significant differences between 4th-5th seeding between each group. It is intersting that despite the differences of 60 days (from Feb. 1 to Apr. 2) in sowing date (from 1st to 5th), blooming varied only 15 days, from June 30 to July 16. This means that, regardless of seeding date, all four groups bloomed by the end of June, and significant differences between each group in 4th-5th seeding seem to suggest that critical temperature for floral bud initiation comes during the period. 2. Number of leaves shows no significant change during 1st to 4th seeding and increased in 5th - 6th seeding. These phenomena could be related to blooming, that is the number of days to blooming seemed to control the number of leaves. With the shifting of seeding date there appeared much differences in number of leaves between the four groups and even between the varieties of same group. Yet, the difference was slight in virginia type tobaccos and significant in broad leaf type. 3. Variations in leaf area also showed much differences between four groups and between the varieties of same group. With the delaying of seeding date leaf area increased significantly in Flue cured tobaccos, increased slightly in the others. 4. Negative correlations were found between leaf weight and leaf area, between the thickness of leaves and leaf area. Leaf area. Leaf areas of Burley tobaccos are similar to those of Flue cured tobaccos, though the thickness of leaves and leaf weight showed the highest values in Flue cured tobaccos, while those of Burley tobaccos showed the lowest values. 5. Yields of tobaccos were affected by leaf area, leaf weight, and the thickness of leaves more than by the number of leaves or days to blooming. Leaf weight showed direct effect to the yield in all four groups. It also showed indirect effect to the yield through the number and thickness of leaves in Flue cured tobaccos, through the number of days to blooming in Native tobaccos, through the number of leaves and leaf area in Turkey tobaccos, and through the number of leaves in Burley tobaccos. As a results, it can be concluded that, the optimal seeding periods are 2nd-3rd, 1st-2nd, 3rd-4th in Flue cured, Burley, Turkey, and Native tobaccos, respectively. 6. Highly positive correlations were found between the thickness of leaves and that of palisade parenchyma+spongy parenchyma: the correlation coefficients were ${gamma}$=0.9562, 0.8809, 0.9696 and 0.9860, in Flue cured, Native, Turkey and Burley tobbaccos, respectively. Over the whole seeding the correlation increased gradually with the delaying of the seeding, though it decreased in 5th-6th seeding when air temperature was high. This phenomenon was more striking in Turkey and Burley tobaccos whose leaves are thin in nature. 7. The ratio of intercellular space increased ti11 4th seeding and decreased thereafter in Turkey and Native tobaccos, while it was highest at 1st seeding and decreased gradually thereafter in Flue cured and Burley tobaccos. 8. With shifting of seeding date the leaf shape indices varied slightly in Buxley tobaccos, while it decreased in Flue cured, Turkey and Native tobaccos. This indicates that growth of leaf length and leaf width varies in ..