STRUCTURE AND PHYSIOLOGY OF PLANTS 19 



grains, and grasses, because their pollen is borne by the wind. 



Cross Pollination. — Plants are said to be cross pollinated 

 when the pollen is taken from one to another by some means. 

 Many of our fruit trees bear much more and better fruit 

 when they are cross pollinated. A number of varieties of 

 apples, pears, peaches, and plums will not bear fruit if grown 

 by themselves. They produce abundant fruit when polli- 

 nated by other varieties of the same class that blossom at 

 the same time. For this reason it is of much benefit to have 

 plenty of bees in the orchard at work gathering their supply 

 of honey during the blossoming season. The owner of a 

 large orchard should have a yard of beehives. The work of 

 the bees gives him a larger crop of fruit as well as a crop 

 of honey. 



Exercise. — Parts of a Flower, — The members of the 

 class should examine a few large, 

 simple flowers and learn to name 

 the parts shown in Fig. 8. 

 United States Farmers' Bulletin 

 408 will be helpful in this exercise. 



Exercise. — Pollination of 

 Corn. — Have students or others 

 bring to school ears of corn on 

 which some of the kernels failed 

 to develop. This shows the result 

 of poor pollination. Perhaps a 

 hot wind injured the silks, or 

 pistils, before the pollen was re- 

 ceived. Other ears may be shown 

 which have sugar-corn kernels 

 mixed with field corn, or have 

 white kernels among the yellow, 

 was carried from other corn plants. Two different kinds 

 of corn should not be planted close together if it is desirable 

 to keep the varieties pure. 



Fig. 8. — Diagram of crois sec- 

 tion of a flower, p, pistil; o, ovary 

 with young seed receiving the pol- 

 len growth; ST, stamens; po, pollen 

 scattering from stamen to pistil; 

 PE, petals; be, sepals. 



These prove that pollen 



