44 



by trees of the same variety, the process is known as self- 

 fertilization and the plant is said to be self-fertile. If, how- 

 ever, these cells must be from different plants, or as in our 

 orchard fruits from trees of different varieties the process is 

 cross-fertilization and the plant is said to be self-sterile. 



If plants are naturally self -fertile the question of poUin- 

 ation is as a rule quite simple ; but if nature demands cross- 

 pollination the problem becomes more involved. There 

 must, in most cases, be some means to prevent self-fertiliza- 

 tion and there must be some agency of transferring the 

 pollen. 



Thomas Andrew Kiiight a famous plant breeder of a 

 century ago concluded from observation and experiment 

 that nature intended the crossing of plants of the same 

 species ; but it required the master mind of Darwin to show 

 the true value of cross-pollination and to work out the many 

 interesting methods nature uses to bring this about. 



Some of the more common methods by which plants 

 avoid self-fertilization are; different periods of ripening of 

 pollen and ovule, difference in length of styles and stamens, 

 the placing of essential organs in different flowers, but the 

 most common is the sterility of the pollen, i. e. the pollen 

 born in a flower is impotent when placed upon the pistils of 

 same flower or upon a flower of the same pomological varie- 

 ty. 



Since our fruit crop depends almost if not altogether 

 absolutely upon pollination and consequent fertilization, it 

 is of vital importance to know the habits of our orchard 

 fruits with respect to this important function. 



Fortunately a few men have seen fit to investigate this 

 problem and I now invite your attention to a brief consider- 

 ation of their work. 



M. B. Waite*acting with the U. S. Dept. of Agriculture 

 made the first extended orchard studies relating to this 

 problem. His first work was with pears and his experiments 

 were conducted about as follows. Strong manila paper bags 

 were placed over clusters of buds and by fastening tightly to 

 fruit spur, all chance of foreign pollen entering was exclud- 

 ed. In order to offset any charge that these flowers were 



►Div. of Veg. Pathology, U. S. Dept. of Ag. Bull. No. 5. U. S. 

 Year Book 1898 



