Abstract
1. In order to increase the efficiency in Cucurbita-cross work, the pollinations in the evening should be considered in comparison with those in the early morning. The author attempted to investigate the ability of pistils and polJen in different ages to effect fruit and seed set, and furthermore to study the physiological changes in pollen and pistils during the time from the evening to the flqwering tiine in the next morning. 2. The ages of flowers, which can be crossed in the evening and in the early morning, are as follows : (a) The ages in the evening : B(the bud stage in the eveni'ng prior to anthesis) ; B , f (the mature condition, that have been artifically kept in the cold condition of about 10'C from the evening to the next fiowerning morning) . (b) The ages in the early morning : b(the early bud stage in the morning of the previous day of, anthesis) . F (the flowering stage) . L (the late stage in the following morning of anthesis) ; F 3. The fruit and seed set in the cross-combinations could be accepted as reliable measure of the fertilizing power of pollen and the receptivity of styles at different ages. 4. In 1951 the percentages of fruit-setting and seed numbers were worse in the cross-combinations of B XB than in those of F xF . The decrease of fruit and seed set in the bud combinations varies with species and varieties. 5. According to fruit setting and seed numbers, the cross-combinations in 1952 are arranged as follows :
