42 FIELD CROPS 



pollen grain grows down from the stigma to the ovary to 

 fertilize the ovule or young 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 tas- 

 sel 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 agents. 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 

 characters of the male and female plants are thus fused 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 are arranged in a compact spike on the cob, 

 which is the 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 



