REPRODUCTION IN PLANTS 79 



92. Self-pollination and cross-pollination. Pollination, 

 we have said, is the transfer of pollen from the anther to the 

 stigma. When the pollen is carried from the anther of a 

 flower to the stigma of the pistil of the same flower, the pro- 

 cess is known as self-pollination. In many of the flowers 

 that are self-pollinated, the anthers are above the stig- 

 mas, and when the pollen is ripe, the anthers burst open and 

 allow the pollen grains to fall upon the stigma or stigmas. 



If pollen is carried from the anther of a flower to the stigma 

 of the pistil of a flower of the same kind but on another plant, 

 this transfer is called cross-pollination. Cross-pollination is. 

 often accomplished by the help of the wind, as in the flowers 

 of the corn, of grasses, and of many trees. In these cases the 

 pollen is dry and light, and the pistils are usually hairy or 

 feathery to catch and hold the pollen grains. 



Most bright-colored and sweet-scented flowers (like the 

 pansy and the clover) are visited by bees or other hairy in- 

 sects which carry pollen on their mouth parts, bodies, and 

 legs from one flower to another, thus insuring cross-pollina- 

 tion. We shall now study the pansy as a type of insect polli- 

 nated flowers. 



93. Adaptations of the pansy for cross pollination. - 

 Laboratory Study No. 45. 



A. Floral envelopes. When there are two circles to the floral 

 envelopes, an outer composed of green parts 

 and an inner made up of brightly colored parts 

 as in the pansy, distinct names are given to the 

 various parts. The outer circle is called the 

 calyx, and its parts are known as sepals; the 

 inner circle is called the corolla, and each of its 

 parts is called a petal. 



1. State the number and color of the sepals. 



2. How many petals are there? Describe the color or 



colors of each. 



