44 BIOLOGY FOR BEGINNERS 



weakens after its store of food has been partly exhausted and the 

 plumule is released. 



Another method of penetrating the soil is found in the corn 

 and in general by those plants whose first leaves are long and 

 slender. In these cases protection is secured by the leaves being 

 tightly rolled into a point and covered by a cap, so that they 

 pierce the soil directly, thus meeting less resistance and securing 

 safety. 



The lifting force of germinating seeds is seldom noticed, but is 

 very great. Masses of earth a hundred times their weight are 

 lifted by our tiny garden seedlings as they come up, forcing their 

 way through the hardest soil. 



The last and most important step in germination is the establish- 

 ment of the young plant in its new environment. In describing 

 this process it is necessary to treat of the development of each 

 part of the embryo by itself. 



The hypocotyl first penetrates the testa. Protected by its root 

 cap and directed downward by gravitation, it begins at once the 

 production of the primary root from its lower end. From this, 

 in turn, the whole root system rapidly develops. The only region 

 of growth is just back of the tip, which, protected by the cap, is 

 safely pushed downward into the earth. 



The cotyledons, as before explained, may rise above ground if 

 the hypocotyl lengthens upward, or, if not, may remain below. 

 In either case they act as a storage of food for the seedling. 



The development of the plumule usually attracts most attention 

 for from it arise the leaves, stem, and, later, the flowers and fruit. 

 It constitutes the shoot of the plant. 



The first organ to develop in germination is the root, because 

 the function required by the seedling is the absorption which the 

 root performs. We shall take up the study of this important 

 organ in the next chapter. 



Many of the statements made in this, and the preceding chapter, 

 can be proven by simple experiments. 



In the first place, the kind of foods stored in the seeds can be 

 proven by the tests described in Chapter IV. 



