CHAPTER III 



THE WORK OF THE ROOTS 



The Roots as anchoring the Plant. The Roots supply the Plant 

 with Water. Roots require Air. Roots can only take in 

 dissolved Material. Etching Action of Roots due to their 

 Excretion of Carbon Dioxide. Elements necessary to the 

 Nutrition of Plants. Plants require Combined Nitrogen. 



The root of the plant has two great functions to 

 perform — one mechanical, in keeping the plant firmly 

 fixed in position ; the other physiological, in supplying 

 the plant with water and the food it requires from the 

 soil. In certain cases, notably the mangold and the 

 carrot among farm plants, the root is also utilised as a 

 storehouse of the reserve material that is being accumu- 

 lated in readiness for the formation of flowers and seed. 

 The books devoted specially to botany must be con- 

 sulted for details regarding the many shapes taken by 

 roots, the manner in which they grow, and the devices, 

 such as the sensitive root-tip, which they possess in 

 order to make their way into the ground and turn in 

 the direction of food and water. For our purpose, the 

 germinated bean and wheat seedlings used for the 

 previous experiments will afford sufficient information 

 as to structure. In the case of the bean, we find a tap- 

 root running straight down, from the side of which 

 secondary roots are thrown off; it may further be 

 observed, when the root has been allowed to grow into 

 damp air, that all the slender roots near the tip are 



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