FRUIT SETTING AS AN ORCHARD PROBLEM 541 



he worked with in England to be self sterile. The degree of self fruitful- 

 ness in the apple varies greatly with the age and vigor of the trees, the 

 season, locality and many other factors. Thus the Jonathan, which is 

 self fruitful in many parts of the United States, is self fruitful in Victoria 

 (Australia) when grown on soils of medium productivity, but self barren 

 when grown on rich soils. '*^ Among the prominent commercial varieties 

 that are classed as comparatively self fruitful, at least in a number of 

 sections, are: Baldwin, Ben Davis, Gano, Jonathan, Oldenburg, Yellow 

 Newtown, Grimes, Wagener, Yellow Transparent, Willow Twig, Esopus, 

 Stark, On the other hand, nearly all of these varieties have been reported 

 partly or completely self barren in certain localities or at certain times. 

 Among those classed as partly or completely self barren are: Arkansas 

 Black, Gravenstein, King, Arkansas, Maiden Blush, Missouri Pippin, 

 Rome, Ralls, Rhode Island, Salome, Tolnian, Wealthy, Winesap and 

 York. These varieties, however, may frequently prove self fruitful. 



Young vigorous trees just coming into bearing have been observed 

 repeatedly to be much more likely to drop their fruit than trees of the 

 same varieties somewhat older and having the bearing habit well estab- 

 lished. On the other hand old weak trees frequently bloom verj'- heavily 

 but set little or no fruit. Often this situation can be remedied by liberal 

 applications of nitrate of soda or some other quickly available nitrogenous 

 fertilizer shortly before blossoming. 



Apple scab and fire blight frequently attack the blossoms or the newly 

 set fruits and are responsible for much dropping at an early stage. These 

 diseases can be controlled by proper spraying and sanitary measures 

 respectively. 



Inter-unfruitfulness has been reported for a few varieties,^^' ^"^ 

 particularly some of those of the Winesap group; but a large body of 

 data indicates that cross sterility is of very little importance in apple 

 production. With perhaps the exceptions just noted the grower may 

 consider it safe to interplant any one variety with any other for purposes 

 of cross pollination, provided they bloom at the same time. 



Parthenocarpy occurs rather frequently, but true parthenocarpic 

 varieties are rare. 



Pear. — The flowers of the pear, like those of the apple, are true her- 

 maphrodites. So far as known, all varieties produce at least a certain 

 amount of good pollen. However, many pear varieties are self barren 

 because of self incompatibility. Waite^^- reported 22 out of 36 varieties 

 as self unfruitful. Among the more prominent of this group are: Anjou, 

 Bartlett, Clairgeau, Clapp Favorite, Columbia, Easter, Howell, Louise 

 and Winter Nelis. Among the more important of the self fruitful 

 varieties are: Angouleme, Bosc, Flemish Beauty, Kieffer, LeConte, 

 Seckel, Tyson and White Doyenne. However, Kieffer has been reported 

 practically self sterile in Virginia'*^ and Bartlett has been found partly 



