NATURE OF PLANTS 



117 



to the advantage of the embryo? Allow the seed to germinate 

 and it will be noted that the absorption of water first causes the 

 embryo to expand and rupture the integument. This is im- 

 mediately followed by the growth and elongation of the lower 

 part of the hypocotyl which results in the pushing out of the root 

 ( Fig. 84, A). Thus it happens that the very part of the embryo 



FIG. 84. Renewal of growth of the bean seed : A, basal region of hypo- 

 cotyl elongating and pushing the root into the soil. B, upper region of the 

 hypocotyl elongating, lifting the cotyledons and epicotyl above the soil. 

 C, hypocotyl erect and epicotyl expanding, forming the first normal leaves. 



that shows the first signs of growth is in close proximity to the 

 water as it enters the seed and doubtless the sheath also assists 

 in retaining water in this region. We are already familiar with 

 the. properties of the root which direct its growth in such a way 

 that no matter how the seed may be placed the root will ulti- 

 mately grow into the soil and toward water and the soil foods, 

 page 54. It is noteworthy that many seeds are so fashioned 

 that they naturally assume such a position on the ground as to 

 bring the root as it emerges into direct contact with the soil. 

 Such an arrangement is equally advantageous for the absorption 

 of water. How many seeds can you find that will naturally 

 lie upon the soil in such a way as to cause the root on emerg- 



