1. Studies on flower bud differentiation and de-velopment of three Spanish types and two Virginia types of peanut varieties were carried out at Hira-tsuka, Kanagawa-ken, from 1948 to 1950.
2. In the Spanish type varieties, the first flower bud primordia was formed on the first node of the primary lateral stem, and it differentiated when the second leaf appeared on the main stem. The flower clusters were formed in succession on the primary lateral stem, but were formed scarecely on the se-condary one.
3. In the Virginia type varieties, the first flower bud primordia was formed on the primary lateral stem at some distance from the base, and it differe-ntiated when the fourth leaf appeared on the main stem. The clusters were formed at intervals on the primary lateral stem but were formed abundantly on the secondary one.
4. Pollen and ovule formation began about 20 days after flower bud differentiation, and they flo-wered still 10 days later (Table 1) .
5. The flower cluster contains several flower buds of various stages of development. Two of them develop more rapidly and bloom earlier than the rest. Under favorable conditions, the remaining three or more buds develop and bloom normally.
6. In Spanish type varieties, 100 or more flower buds were formed about one month after the plan-ting, although only about 30 buds were formed in Virginia type varieties.
7. The flower buds formed at an early stage of the growth developed more vigorously, and also-they flowered and fruited more favorably than those formed at a later stage.
8. In Virginia type varieties, the number of flo-wer buds was greater on the second lateral stem than on the first one, but that of fruits was grea-ter on the first one as in the case of Spanish type varieties.
9. The application of nitrogenous fertilizer at an early stage of the growth, determination of planti-ng time and selection of varieties in peanut culture are discussed, based on the above facts.