CHAPTER III. 



GROWTH OF ROOT AND STEM. 



31. Direction of growth. In studying the germination of 

 seeds one fact becomes very evident which perhaps was familiar 

 before, that the root grows downward and the stem upward. This 

 is very important for the plant in order 

 that its parts may establish a congenial 

 relation to their surroundings, and be in 

 a position to perform their work ; the root 

 in the ground and the foliage shoot in the 

 air and light. When seeds are scattered 

 by natural means or are sown by the 

 farmer or gardener they fall in various 

 positions. The seed may lie so that the 

 embryo is upright and the root already 

 pointing in a downward direction, or it 

 may be horizontal or inverted. Neverthe- 

 less, the root when it emerges from the 

 seed turns downward to enter the soil, and 

 the stem turns upward. Some seeds which 

 are carried by the wind are so balanced 

 that the root end of the embryo hangs 

 downward (many composites, the clematis, 

 etc., see chapter on seed distribution). 



32. Region of elongation in roots. 

 -The region where elongation takes 

 Pumpkin seedlings, the root place in roots is determined by a careful 



marked in left. Right one show- , . r , . , i_ r 



ing where growth took place in plotting OI the TOOt into a number OI 

 twenty-four hours. . i i i . i j 



small sections, and by keeping the seed- 

 ling in an upright position in moist air. Subsequent observa- 

 tions and a careful plotting of the root from day to day shows 



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