FERTILIZATION 



2\)W 



Figure 309. — Swallow-tail Butterfly 

 Pollinating Persian Lilacs. 



of the stalk. The style of each pistil protrudes from the 



ear of corn as a long green thread, called the silk. The 



pollen is light and abun- 

 dant, and falls from the 



stamen with every stir 



caused by the wind. 



The stigma at the end 



of the style is sticky, 



as in the bean. In a 



field of corn where 



many plants are shed- 

 ding pollen at the same 



time, it is almost certain 



that every pistil will 



receive at least one 



grain of pollen. It is to secure thorough pollination that 



corn is planted in fields, with the plants close together. 



Plants which have both sta- 

 mens and pistils on them, but 

 on different flowers, are called 

 monoecious (mo'ne'shfis : Greek, 

 monos, one ; oikus, house). Plants 

 which have only staminate or 

 only pistillate flowers are calif 1 

 dioecious (di-e'shus: *//. twoj 

 oikus). 



222. Fertilization. — The second 

 step in the production of a ^'kh\ 

 is fertilization. By this we mean 

 the union of the sperm DUCleUfi 

 of the pollen cell ( male parent ) 



with that of the egg cell in the ovule (female parent ). 

 The pollen grain has two coats, an outer ami an inner. 



The outer is thicker than the inner, but it has thin spots 



Figure 310. — Corn Flower 

 with Pistils. 



