4 6 



FUNDAMENTALS OF AGRICULTURE. 



and the pistil is thus fertilized by pollen from the same 

 flower, i. e., is close-fertilized or self-pollinated. This 

 is generally the case with wheat, oats, peas and many 

 other plants. Mostly, however, the pollen is not set 

 free till the flower opens. Frequently, perhaps, in the 

 majority of cases the stigma is not ready to receive 

 pollen at the same time that the pollen in that flower 

 is being shed, so that self-pollination is avoided. 



RASPBERRY-BLACKBERRY HYBRID " PRIMUS " AND PARENTS. 

 California dewberry, female parent; Siberian raspberry, male parent. 



Some plants, indeed, are sterile to their own pollen 

 and require pollen from a different plant of the same 

 kind. Such plants of course are especially dependent 

 upon insects. Some varieties of pears and other fruits 

 which are propagated by budding or grafting, are 

 sterile to pollen from the same variety, so that plants 

 of other varieties of the same fruit have to be set 

 among them to insure fruitfulness. 



Hybridization. Ordinarily, in the natural course 

 of events, it is only when pollen of the same species 

 of plant reaches the stigmas that seed formation oc- 



