36 THE ESSENTIALS OF AGRICULTURE 



it has developed a root system and unfolded its leaves in the 

 air and light, and is able to get food from the soil and air. 



If a grain of corn be softened by soaking it in water for a day 

 or two, the germ can easily be removed. If this germ is planted 

 it will not grow, because it has been robbed of its supply of 

 food and the protection which the seed coats afford. If a bean 

 be soaked in water and then opened, it will be seen that the 

 halves are held together by the central part of the embryo. In 

 fact, the halves are the seed leaves of the embryo, and are 

 much larger and thicker than the rest of the plant because 

 it is in them that the food for the young plant is stored. 

 When these thick seed leaves are removed from the embryo 

 it will not grow well, for the same reason that the corn germ, 



or embryo, without 

 the rest of the grain 

 would fail to grow. 



\Embryo Embro 39. The embryo. 



The embryo, or the 

 A B undeveloped plant 



FIG. 18. Corn and bean embryos as it exists in the 



A, corn grain with embryo removed ; B, bean embryo Seed before growth 



begins, consists of 



three parts the seed leaves, or cotyledons (Fig. 18), which nour- 

 ish the young plant ; the bud, or plumule, which grows into the 

 stem and leaves ; and the radicle, which develops into the root. 

 40. Requirements for germination. Seeds cannot germinate, 

 or sprout, unless they are supplied with moisture, air, and the 

 proper temperature. The first step in germination is the absorp- 

 tion of water. When the stored food in the seed becomes moist 

 and the temperature is favorable, the food is converted into 

 sugar through the activity of ferments, or enzymes. Closely fol- 

 lowing the formation of sugar, the cells of the embryo begin to 

 swell and grow, and the little plant soon becomes large enough 

 to break the seed coat. Seeds will pass through the first stages 

 of germination even though submerged in water. They soon 

 stop growing, however, and die for lack of air. Death is quickly 



