11J3 Elementary Principles of Agriculture 



sterile to their own pollen. Many varieties of grapes 

 also do not set fruit when pollinated with their own 

 pollen. The illustration facing page 115 shows the 



Fig. 58. Injurious effect of self-pollination shown in pile at right. Alter 

 Hartley, United States Department of Agriculture. 



effect of pollen of several varieties of grape on the 

 Herbert grape. Some varieties make good pollinizers 

 while others do not. If one is planting Herbert grapes, 

 other varieties should be planted nearby to furnish 

 pollen. In the same way, an orchard of Kieffer pears 

 will be more fruitful if trees of other varieties are in 

 the orchard. The bees will carry the pollen back and 

 forth as they go from flower to flower. Sometimes in 

 long-continued rainy weather during the flowering sea- 

 son a full crop of fruit is not set, because the bees are 

 unable to visit the flowers freely. 



172. Not All Plants Pollinated by Insects. Some plants, 

 like wheat, oats, cotton, beans, etc., are ordinarily self- 

 pollinated, that is, the pollen in the flower is produced 

 so that it naturally falls on the stigma. Many other 

 plants, as the pine trees, field corn, willows, etc., are 

 solely dependent on the wind to carry the pollen from 

 one flower to another. There are many interesting 

 adaptations for bringing about pollination, which cannot 

 be discussed here. 



