Abstract: The present study was carried out both in the greenhouse and in the field of the experiment farm of this institute in Hangchow during the years 1954–1956. An attempt was made to investigate the effect of various treatments of vernalization and photoperiod on the flowering and vegetative growth of Chinese cabbage and mustards, and on the interaction of photoperiod and temperature. Chinese cabbage herein studied included both the headed varieties (Brassica pekinensis Rupr.), and non-headed varieties (B. chinensis L.). The varieties of mustards (B. juncea Coss.) included those grown for their abundant radical leaves, and those for their swollen fleshy roots or stems. They were collected from many geographic regions of China. The common cabbage (B. olcracea var. capitata L.) and Chinese kale (B. o. var. acephala subvar, alboglabra Burkill) were also used in this study. From the result of the present experiment, it was found that almost all the varieties herein studied of both Chinese cabbage and mustards may complete their stage of varnalization by lowtemperature treatment of sprouted seeds. The varieties of each species, cabbage or mustard, may further be generally separated into winter type and spring type according to their responses to vernalization and photoperiod. The “spring” varieties may flower in the same season after seed sowing, without a definite period of low temperature treatment; while the “winter” varieties have to pass through a definite period, generally 20–30 days, of vernalization treatment. The common cabbage did not produce flowers in the same growing season even if it bad been exposed for a certain period to low temperature treatment either of the sprouted seeds or of the plants being too young to be affected by the treatment. The Chinese kale which taxonomically belongs to the same species of common cabbage, may produce flowers without exposure to a low-temperature treatment under Hangchow condition. Obviousely, the plants which may complete their vernalization stage by the sprouted seeds, may also complete this stage by growing plants, but the reverse was not the case. The temperature favourable for the completion of vernalization of both Chinese cabbage and mustards was not very low. No appreciable differences were found in the number of days required to flower between the lots vernalized at 0–3℃, and those at 6–8℃. The duration of vernalization of the “winter” varieties of both Chinese cabbage and mustards lay between 20 and 40 days at 0–3℃. They would produce no flowers as the unvernalized seeds were sown on April 9,1956, under Hangchow climatic and soil conditions. But the “spring” varieties of non-headed Chinese cabbage and mustard’s collected from South China, produced flowers in the same season after sowing, without any low-temperature treatment. The number of days required from seeding to flowering decreased with increasing the duration of vernalization from 5 to 60 days. But the influence by the duration of vernalization on the “spring” varieties was not so pronounced as on the “winter” varieties. Some varieties of Chinese cabbage was able to complete the stage of vernalization in 5 days at 0–3℃, while others were in need, of 20 to 30 days at least. All the varieties of Chinese cabbage and mustard were found to be of long day plants. Flowering may be accelerated by increasing the day length, but there, were great differences of photoperiodic responces among different varieties. In one experiment carried out on 1956, the vernalized seeds of Tzu Tsai Tai (B.chinensis) and Hsueh Li Hung (B. juncea) sown on July 11, required much more days to flower than that sown on April 9. Apparently too high a temperature (30℃ or more) during the photoperiodic exposure may retard the flower development of both Chinese cabbage and mustard after vernalization treatment. Moderate cold nights (15–20℃) may accelerate the photostage. Not only did the photoperiod and temperature influence the flower development of a given variety, but also influence the height of the plants, the size and shape of the leaves and even the structure of the flower organs. Chinese cabbages were found to be generally more pronouncedly affected , by these factors than mustards.