34 



directly. The average of their answers is four- Some said 

 "the fewer the better", "not many", "few", etc. The answers 

 on the whole show clearly that the successful growers realize 

 the importance of not planting too many varieties. The grow- 

 ers who have large orchards usually want enough trees of each 

 variety to enable them to market that variety in car-load 

 lots, rather than to be forced to ship in mixed car-load 

 lots. Therefore the larger one's orchard the greater may 

 be the number of varieties planted. 



Again, different varieties sometimes require differ- 

 ent methods of treatment; especially does this apply to the 

 operations of spraying. Therefore, it sometimes becomes 

 difficult to handle an orchard to the best advantage when 

 the varieties are very much mixed. 



There is an important advantage to be derived from 

 mixed planting which should not be overlooked in this con- 

 nection. It is a recognized fact that certain varieties 

 under certain conditions will not set fruit when planted 

 alone in large blocks. Some varieties are self -sterile, 

 that is, the pistil of the flower will not become fertiliz- 

 ed by pollen from this flower or other flowers of this var- 

 iety. The causes which influence self-sterility are not 

 understood. A number of valuable experiments have been 



