172 GERMINATION 



occupies a third of the length of the bean in Fig. 309. The 

 hilum and micropyle are always present in seeds, but they 

 are not always close together. In many cases it is difficult 

 to identify the micropyle in the dormant seed, but its location 

 ^ is at once shown by the protruding caulicle 

 as germination begins. Opposite the micropyle 

 in the bean (at the other end of the hilum) is 

 External parts of an elevation known as the raphe. This is 

 bean. formed by a union of the funiculus or seed- 



stalk with the seed-coats, and through it food was transferred 

 for the development of the seed, but it is now functionless. 



335. Seeds differ wonderfully in size, shape, color and 

 other characteristics. They also vary in longevity. These 

 characteristics are peculiar to the species or kind. Some 

 seeds maintain life only a few weeks or even days, whereas 

 others will "keep" for ten or twenty years. In special cases, 

 seeds have retained vitality longer than this limit, but the 

 stories that living seeds, several thousand years old, have 

 been taken from mummies are unfounded. Oats do not 

 retain their vitality for more than a year or two. Seed of 

 alfalfa may retain its vitality for eight years or more. The 

 condition of storage of the seed is an important factor in 

 the retention of seed vitality. Moisture is especially dele- 

 terious; a dry atmosphere of the storage room is necessary 

 for maintaining the vigor of the seed. 



336. Germination. — The embryo is not dead; it is only 

 dormant. When supplied with moisture, warmth, and oxy- 

 gen (air), it awakes and grows: this growth is germination. 

 The embryo lives for a time on the stored food, but grad- 

 ually the plantlet secures a foothold in the soil. The roots 

 absorb and the leaves elaborate food and the seedling is inde- 

 pendent with respect to its food supply. When the plantlet 

 is finally able to shift for itself, germination is complete. 



337. The germinating seed first absorbs water, and 

 swells. The starch and other stored foods are transformed 



