SYSTEMS OF TISSUES AND PLANT GROWTH. 



167 



represented by the Oak, 

 Pine, Elm, Maple, Apple, 

 Pear, Peach, Cherry, and 

 other fruit and timber 

 trees. 



420. The root is that 

 part of the plant that 

 grows downward into the 

 ground and holds the 

 whole firmly in the soil. 

 Its tissues correspond with 

 those of the stem to which 

 it belongs, and it increases 

 in diameter by additional 

 layers, one for each period 

 of activity, succeeded by 

 a rest. The extremity of 

 the root and that of each 

 of its branches is encased 



519 



520 



519, Rootlet of Maple with hairs or fibrillae; , root 

 cap. 520, Duckmeat, showing the root cap . 



518, a, Shrub; b, Fir; c, Oak-tree. 



by a layer of older cells, 

 called the root .cap, a con- 

 trivance which seems to 

 be intended to protect the 

 tender infant cells just be- 

 hind it, which during the 

 growing season are increas- 

 ing and multiplying, to ex- 

 tend the root and rootlets 

 in all directions in the soil. 

 The parts of the root and 

 rootlets near the growing 

 points absorb the fluids 

 which are presented to 

 them in the soil, but this 



