38 INJURIOUS EFFECTS OF PREMATURE POLLINATION. 



by the pistil, as shown by b, fig. 1, and by the time the pistil straight- 

 ens and exposes its stigmatic surfaces the stamens have assumed a 

 recumbent position and have drooped their anthers, as shown by c. 

 The modifications of this proterandrous flower successfully prevent 

 self-fertilization and premature pollination without interfering with the 

 proper shedding of pollen. 



The man}' adaptations of flowers to insure pollination at a certain 

 time is interesting and suggestive of the importance to be attached to 

 the time for applying pollen when hand-pollinating. Movements on 

 the part of stamens so as to bring the pollen to the pistil at a certain 

 stage in the growth of the flower, and especially movements on the 

 parts of the pistils themselves which bring the stigmas into contact 

 with the stamens, are admirable adaptations. With some flowers, such 

 as those of corn, the pistils have no definite length, but continue to 

 grow in search of pollen, as it were. If pollinated upon protruding 

 from the husks, corn silks perform their functions, turn brown, and 

 become dry without making a growth of more than 2 or 3 inches 

 beyond the end of the ear, but if kept secluded from pollen they will 

 continue to grow for a week and will attain a length greater by 14 or 

 more inches than would otherwise have been the case. 



During the work with the various flowers herein mentioned nothing 

 has been more noticeable than the individuality possessed by flowers 

 of different forms. It seems impossible to say that the flowers of one 

 plant will respond in a given manner because those of another plant 

 so respond. From these experiments it is evident that flowers of dif- 

 ferent genera of the same order, as the tomato and tobacco, respond dif- 

 ferently to the effects of premature pollination, while the flowers of 

 Datura tatvla, of the same order, suffer as do those of tobacco, but do 

 not fall. 



Two of the five kinds of flowers experimented with mature their 

 pistils before their stamens and were uninjured by premature pollina- 

 tion, while the three that mature their anthers and stigmas at the 

 same time were injured. It is perhaps accidental that such is the 

 case with these five flowers, but it is to be hoped that future work will 

 reveal some means of distinguishing flowers that will, from those that 

 will not produce seed when prematurely pollinated. For the plant 

 breeder it is quite important to know with what flowers one can apply 

 the pollen at the time of emasculation and thus avoid the extra labor 

 of removing the bags, pollinating, and again bagging the flowers when 

 the pistils have become receptive. 



It is apparent that several of the phenomena suggested by the 

 results of these experiments have not been sufficiently proven. How- 

 ever, concerning the following points the writer feels no doubt: 



That the application of good tobacco pollen to immature tobacco 

 pistils causes the flowers so treated to fall from the plant because of 

 the growth of pollen tubes into their ovaries; 



