CHAPTER VIII 



ROOTS THEIR STRUCTURE AND FUNCTION 



Vocabulary 



Constitute, to forri part of. 



Immersed, covered by water. 



Adventitious, growing at unusual places. 



Retain, to hold. 



Epidermis, the outer layer of plant or animal tissues. 



Cortex, a spongy layer under the epidermis of roots. 



Cambium, region of active growth in root or stem. 



The. developing seedling consists primarily of the root and 

 the shoot. The latter bears the buds, leaves, flowers, and fruit, 

 while the root, usually hidden and unnoticed in the soil, plays an 

 equally important part in furnishing food and stability to the 

 plant. 



Characteristics of Roots. The root differs from the stem in the 

 following points: 



Root Stem 



Bears no leaves or flowers. Bears leaves and flowers. 



Grows irregularly. Grows by definite nodes. 



Growth mostly at tip. Growth in each internode. 



Tip protected by cap. Tip protected by scales. 



Branching very irregular. Branching regular. 



Turns toward gravity. Turns away from gravity. 



Branches start internally. Branches external. 



Root System. When a plant is pulled from the soil, the root 

 system is exposed. This may consist of one long central portion, 

 the primary root, from which many secondary branches grow; 

 or it may be a fibrous mass of small roots with no apparent primary, 



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