BOTANY 



dividing, so increasing their number, and a longer part 

 still further back is marked by the enlargement of the 



cells in all directions, but 

 most notably longitudinally, 

 while their vacuoles are being 

 formed. These regions are 

 known as the root cap, the 

 region of cell division, and 

 the region of cell growth. 

 Little more can be distin- 

 guished at this stage. 



A little later, when the ex- 

 ternal band of root hairs 

 appears, preparation for the 

 discharge of particular duties 

 by the different parts begins 

 to be indicated, while the 

 requirements of the life of 

 the organ involve further 

 adaptations. The first of 

 these is the admission of air 

 to the interior to supply the 

 oxygen all living substance 

 needs to breathe. The com- 

 mencement of the formation 

 of an aerating mechanism 

 can be traced all through the 

 young embryo, even at this 

 age ; as seen in an older root 

 it consists of the splitting of 

 the cells apart from one 

 another at some point of 

 each, frequently at the angles 

 their walls make with each 

 other (Fig. 12). These little splittings make a number 

 of spaces between particular cells, and as growth goes on 



FIG. ii. Longitudinal section of 

 young root. Xao. 



