Self-sterility 157 



days of sunshine. It is probable that pollen is more 

 potent in some years than in others. 



There is yet insufficient positive knowledge of the 

 inter-pollination of fruits, and no subject connected with 

 pomology is in greater need of further study. We know 

 that many of the most productive orchards are of 

 many varieties, and that some varieties sometimes refuse 

 to fertilize themselves. The most positive knowledge on 

 the impotency of pollen amongst our common fruits is in 

 connection with the plums of the Wild Goose type, with 

 sweet cherries, and with many grapes. The safest practice, 

 in all fruits, is to plant only a few rows of any one variety 

 together of fruits in which self -sterility is a frequent char- 

 acteristic. The chief point to be observed in choosing the 

 varieties is that they shall bloom together. 



Strawberries often lack stamens altogether, while 

 others have so few and so poor stamens that they are 

 practically self-sterile. Ordinarily, there should be a row 

 of a perfect-flowered variety for every two rows of a 

 pistillate or infertile variety of strawberry. 



Some kinds of red raspberries are only partially self- 

 fertile, and should therefore be grown in mixed planta- 

 tions. Cuthbert is apparently strongly self-fertile and 

 is probably a good pollinizer. 



The early experiments in this subject by Waite and 

 others gave the following lists of self -sterile and self-fertile 

 fruits : 



Pears. Varieties more or less self-sterile. Angouleme, Anjou, 

 Bartlett, Boussock, Clairgeau, Clapp, Columbia, De la Chene, 

 Doyenne Sieulle, Easter, Gansel Bergamotte, Gray Doyenne, 

 Howell, Idaho, Jones, Kieffer, Lawrence, Louise Bonne, Mount 

 Vernon, Pound, Sheldon. Souvenir du Congres, Superfin, Wilder, 

 Winter Nelis. 



Varieties usually self-fertile. Bosc, Brockworth, Buflum, Diel, 



