26 INJURIOUS EFFECTS OF PREMATURE POLLINATION. 



EXPERIMENTS WITH TOMATO BLOSSOMS. 



The work so far having been performed on flowers the pistils of 

 which are naturally protected against a premature pollination, it was 

 desired to try some flower the stigma of which is naturally exposed to 

 pollination before it is receptive. It is to be supposed that flowers of 

 the latter kind would not be killed by premature pollination as tobacco 

 flowers are, for nature could not expose the young flowers to so immi- 

 nent a danger of destruction without the plant becoming extinct or its 

 manner of flowering changed by natural selection. The tomato blos- 

 som was found to present the conditions desired, for here the young 

 stigma is exposed more or less for two or three days before it is 

 receptive. (See PI. IV, fig. 9.) 



All of the work on tomato flowers was performed in the greenhouse, 

 where there were grown eight different varieties. These vines grew 

 very vigorously and were pruned and trained to vertical wires as the 

 growth proceeded. Near the conclusion of the work the vines had 

 reached a height of 8 or 9 feet and had such a mass of foliage that 

 pruning was frequently necessary. The following notes of the 

 25 experiments performed with tomato blossoms are given in about 

 the words written in the notebook as the work progressed. Some 

 explanations and references to figures are inserted, and to avoid too 

 many repetitions the wording has been changed in some places, and 

 the description of the kind of blossom buds chosen is omitted except 

 in experiments 1 and 5. Experiment 5 was performed on fully open 

 flowers, as explained in the notes of that experiment. The kind 

 of blossom buds chosen for all the other experiments is explained in 

 the notes of experiment 1 and illustrated by PI. IV, fig. 10. Fig. 11 

 of the same plate shows another of the same age which has been decap- 

 itated, and fig. 12 one of same age that has been emasculated. It 

 will be noticed that decapitation prepares the flower for premature 

 pollination just as well as emasculation, but this process of decapita- 

 tion can not be used in hvbridization work since there is dano-er of the 

 flower becoming self-fertilized by the pollen remaining in the decapi- 

 tated flower. The flowers were usually simply decapitated because 

 decapitation was more quickly performed and perhaps of less injury 

 to the flowers, although the experiments do not show any injurious 

 effects from emasculation (decapitation employed in experiments 3 and 

 4, and emasculation in similar experiments 7 and 9). (See Table IV, 

 p. 35.) However, in all experiments where it was necessary to remove 

 all of the pollen the flowers were decapitated and then emasculated. In 

 some cases one experiment is an exact repetition of another, while in 

 other cases it is a repetition so far as practical results are concerned, 

 but different in minor details, as, for example, in the variety of tomato 

 from which the pollen was taken. In all these experiments, except 

 experiment 5. the flowers and resulting fruits were kept covered with 

 paper bags from the commencement of the work until the fruit was ripe. 



