FERTILIZATIOl^ 41 



from the stigma to the ovary to fertihze the ovule, or youno; 

 seed. On most plants, both stamens and pistils are on the 

 same plant and are parts of the same flower. In corn, the 

 stamens are borne in the tassel, while the pistillate flowers 

 are in the ear, the silks being the styles and stigmas of the 

 pistils and the young kernels the ovaries. In some flowers, 

 as in the grasses, the calyx and corolla are replaced by scales 

 or are wanting. A typical flower in which all the parts are 

 readily seen is that of flax. 



44. Fertilization. When the ovules are ready for ferti- 

 lization, the stigma becomes moist and sticky so that it 

 catches and holds the pollen grains that come in contact 

 with it. The anthers open and shed their pollen. It may 

 fall directly upon the moist stigmas, or be carried there by 

 the wind, by insects, or by other agencies. In any case, a 

 pollen grain germinates and grows down the slender tube of 

 the pistil from the stigma to the ovary, where it fertilizes the 

 ovule. The ovule then develops and eventually matures 

 into a seed; if it is not fertilized, it withers away. The char- 

 acters of the male and female plants are thus united in the 

 embryo of the seed. The ovary may contain one, several, 

 or many seeds. In the grains and grasses, it contains one; 

 in flax, several, usually five, seeds are produced; in some 

 weeds, notably purslane, or "pussly," the number of seeds 

 produced by one flower runs into the hundreds. The grains 

 of corn each represent a flower, of which the silk is the pistil. 

 The flowers form a compact spike on the cob, or rachis. 



45. Close and Open Fertilization. When a flower is so 

 constructed that it is normally fertilized by its own pollen, 

 it is said to be close-fertilized. Such are the flowers of oats, 

 wheat, barley, and many of the grasses, many of which are 

 fertilized before the flowers open. Different varieties of 

 these plants may be grown side by side without danger of 

 mixing. An open-fertilized flower is one that may be ferti- 

 lized by pollen from another flower either on the same plant 



