10 INJURIOUS EFFECTS OF PREMATURE POLLINATION. 



pollen, and further, that pollen tubes are found penetrating the styles 

 and ovaries of the fallen flowers, give good reasons for the statement 

 that the application of pollen to the pistils of some flowers before the 

 pistils are mature enough to receive the pollen produces an injury 

 which results in the death of the flowers. 



In working with the different kinds of flowers herein mentioned, 

 except Datura tatula, the following method was employed: Ten simi- 

 lar flower buds were selected and treated in exactly the same manner 

 and labeled by means of numbers, the ten flowers of each experiment 

 bearing the same number. When the results were to show the effects 

 of the different methods of treatment, the experiments were per- 

 formed at the same time and on similar flowers equally distributed on 

 the same plants. This made all conditions alike for the experiments 

 to be compared, except the treatment of the blossoms. 



At the end of the remarks regarding each kind of flower, a table is 

 given describing all the experiments with that flower. In these tables, 

 as elsewhere, the experiments are designated by the original numbers 

 attached to the flowers when the work w T as begun. 



EXPERIMENTS WITH TOBACCO BLOSSOMS. 



The conclusions in regard to the work with tobacco blossoms are 

 drawn from the behavior of 670 hand-pollinated flowers of Cuban 

 tobacco {Nicotiana tahacum). The different questions or phases of the 

 work were tested by experiments consisting in every instance of 10 

 similar flowers, making in all 67 experiments. Quite often several of 

 these numbered experiments were exact repetitions and as such theit 

 results compare favorably. By combining these like experiments we 

 get results based upon work with larger numbers of flowers. Thirty- 

 two of the 67 experiments, while throwing light on the questions here 

 considered, were made primarily for the purpose of settling other 

 questions and to test the longevity of tobacco pollen, and so will not 

 be referred to in this article. This will explain why the experiments 

 with tobacco blossoms given in Table I are not numbered consecutively. 

 It may be mentioned here that pollen that had been kept in tinfoil for 

 three months, while still capable of producing germinative seeds, was 

 not so destructive to immature pistils as was fresh pollen, perhaps 

 because the old dry pollen germinated less readily on the young stig- 

 mas before the exudation of stigmatic fluid which indicates the recep- 

 tive period. At one time it was thought that this explanation was 

 corroborated by the fact that no seed pods resulted from pollen two 

 months old when used on mature flowers in the field, while pollen three 

 months old gave good results on similar flowers in the greenhouse. It 

 was thought that perhaps the dry pollen germinated with greater ease 

 in the moist greenhouse. Such may have been the case, but it is now 

 thought that the hot summer weather affected the pollen. The pollen 



