THE SEED 165 



is the hilum. It occupies a third of the length of the bean 

 in Fig. 283. 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 be- 

 gins. Opposite the micropyle in the bean 

 (at the other end of the hilum) is an eleva- Extemafparts of 

 tion known as the raphe. This is formed bean> 

 by a union of the funiculus or seed -stalk with the seed- 

 coats and through it food was transferred for the develop- 

 ment of the seed, but it is now functionless. 



308. 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 live seeds, several thousand years old, 

 have been taken from mummies are unfounded. 



309. GERMINATION. The embryo is not dead: it is 

 only dormant. When supplied with moisture, warmth, and 

 oxygen (air), it awakes and grows: this growth is germina- 

 tion. The embryo lives for a time on the stored food, 

 but gradually the plantlet secures a foothold in the soil 

 and gathers food for itself. When the plantlet is finally 

 able to shift for itself, germination is complete. 



310. The germinating seed first absorbs ivater, and 

 swells. The starchy matters gradually become soluble. The 

 seed-coats are ruptured, the caulicle and plumule emerge. 

 During this process the seed respires freely, throiving off 

 carbon dioxid (062). Fill a tin box or large-necked bottle 

 with dry beans or peas, then add water; note how much 

 they swell. , Secure two fruit -jars. Fill one of thorn a 

 third full of beans and keep them moist. Allow the 



