P R E F A C E 



The importance which plant breeding has assumed in the improve- 

 ment of varieties of cultivated plants makes it desirable that careful 

 attention be given to every detail involved in the production of 

 hybrids. The accompanying paper, by Mr. Charles P. Hartley, assist- 

 ant in physiology in the Plant-Breeding Laboratory, Vegetable Patho- 

 logical and Physiological Investigations, is the result of a study of the 

 effects of premature pollination in its relation to the setting of fruit. 

 The investigation has demonstrated the decidedly injurious effect of 

 premature pollination in several cases, and the fact is emphasized that 

 in order to secure successful results in the production of hybrids and 

 the setting of fruit, careful consideration must be given to the time 

 when pollen should be applied to the stigma. It is believed that the 

 results here presented will be of service to investigators and to workers 

 in plant breeding. 



Albert F. Woods, 



Pathologist and Physiologist. 

 Office of the Pathologist and Physiologist, 



Washington, D. 6'., May 21, 1902. 



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