THE ROOT | ie) 
In the case of the root, as in that of the stem, the portion 
that is in the phase of formation grows slowly. At the end 
of the phase of formation the rate of growth increases, and 


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Fig. 182. Longitudinal section of a tip of an onion root 
The growing point is in the center of the drawing and consists of three regions : 
one which produces the rootcap, one which gives rise to the cortex and epidermis, 
and one which forms the stele. (x 270) 
continues to increase until the most rapid rate is reached during 
the phase of elongation. After this the rate of growth in length 
again decreases until, at the end of the period of maturation, 
growth ceases altogether. Growth is therefore most rapid not at 
the tip but slightly back of the tip in the region of elongation. 

