36 



PLANT GROWTH 



The growth in length of the root and its pushing through 

 the soil has been of interest to many. Darwin tried to 

 figure the energy necessary for a root to enter the soil and 

 in his investigations did find that it grows with a rotating 

 motion, which enables it to go through the softer areas or 



Region of 

 cell division' 



Region of 

 elongation 



Root cap 



Fig. 11. Enlarged view of the end of a root, showing root cap, growing region and 

 root hairs. (From Transeau, Sampson and Tiffany, Textbook of Botany, Harper and 

 Bros., 1940.) 



Openings in the soil. The force, more recently, has been 

 found to be derived from osmotic pressure. 



The growth in length, shown in the section of Figure 10, 

 takes place within a quarter of an inch, just back of a group 

 of tough cells called the root cap, often visible with the eye. 

 The growth area may be divided into two regions; the grow- 

 ing point where the cells divide, which is about one-thirty- 



