FRUIT BREEDING 271 



Knight (1917) has made a study of self-sterility in the apple and 

 the conclusions reached show the manifold causes which must be 

 considered in a study of the problem. For this reason the 

 conclusions are here given verbatim. 



"1. Self -sterility in Rome Beauty is not due to sterility of the pollen 

 as has been shown to be the case in certain varieties of grapes. 



"2. Sensitiveness of pollen to over-abundant moisture supply is not 

 involved here as a factor, as has been shown by Jost for the pollen of 

 many grasses, barley especially; and by J. N. Martin for the pollen of 

 red clover. The pollen of Rome Beauty and many other varieties 

 germinated in distilled water. 



"3. Rome Beauty stigmatic fluid extracts offer no inhibition to the 

 germination and growth of Rome Beauty pollen. 



"4. Rome Beauty stigmas offer no particular mechanical obstruction 

 to the penetration of Rome Beauty pollen tubes. 



"5. Self -sterility of Rome Beauty is not due to inability of its own 

 pollen tubes to grow deep enough to reach the egg. This has been sug- 

 gested as the cause of self-sterility in certain pear and apple varieties 

 by the work of Osterwalder. 



"6. From present indications one important factor in self -sterility 

 of Rome Beauty is the relatively slow rate of growth of Rome Beauty 

 tubes in Rome Beauty stylar tissue. Doubtless other factors will be 

 found upon further examination." 



Inheritance of Some Characters. The mode of inheritance 

 of most fruit characters has as yet not been determined. There 

 are, however, numerous experiments under way for the purpose of 

 learning how individual characters behave in crosses. The lack 

 of information in this field is due to the heterozygous condition 

 of many fruit varieties and to the fact that with many fruit crops 

 so long a period elapses between the time of sowing the seed and 

 the production of fruit. 



Apple. Inheritance in the apple is well illustrated by a 

 study made at the Geneva Station by Hedrick and Wellington 

 (1912). Crosses were made in 1898 and 1899 and 148 seedlings 

 were grown. In 1912, 106 of the seedlings had come into bearing. 

 These 106 seedlings resulted from 11 crosses. The first genera- 

 tion naturally does not furnish very reliable data as a means of 

 deciding the mode of inheritance of individual characters. 



Three types of skin color were studied, red, yellow, and inter- 

 mediates. The conclusion was reached that Ben Davis and 

 Jonathan were both pure for red color of skin, as crosses between 



