124 



GROWTH OF THE SEED 



very part of the embryo 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 al- 

 ready 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 ultimately grow into the soil and toward water and 

 the soil foods, page 57. 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 



Fig. 84. Renewal of growth of the bean seed: ^ , basal region of hypocotyl 

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

 cotyl elongating, lifting the cotyledons and epicotyl above the soil. C, hypo- 

 cotyl erect and epicotyl expanding, forming the first normal leaves. 



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 

 emerging to be directed away from the earth? Thus at the very 

 start the growth of the seed is of such a character that the young 

 plant is anchored to the soil by the root and brought into proper 

 relation with the water and other materials necessary for the 

 construction of foods. As soon as this work is well under way 

 the upper end of the hypocotyl begins to elongate, pushing up 



