96 



BOTANY 



food stored in its root enables it to get an early start in the spring, 

 so as to be better able to produce seeds when the time comes. 



Cross section of parsnip. The 

 cortex (C.) is given up almost 

 entirely to the storage of 

 food. Note the medullary 

 rays (M.R,) which radiate 

 from the center of the wood 

 iW.). 



Fascicled roots (dahlia) ; fibrous roots which 

 have become thickened with stored food. 



Examples of other roots storing food nre carrot, radish, yam, 



sweet potato, etc. Demonstration. — Test a cross section 



of the parsnip root with iodine. In 

 which part of the root is starch stored? 

 Test another cross section with nitric 

 acid and ammonia. Which part of the 

 root contains stored food? 



Water Roots. — In the duckweed, a 

 plant living in water, the roots are short 

 and contain few root hairs. The water 

 supply is so great that few root hairs 

 have been called forth. The water hya- 

 cinth is another example of slight de- 

 velopment of roots. The plant is 

 buoyed up by the water and does not 

 need strong roots to held it firm. 



Adventitious Roots. — Roots are 

 often developed in unusual places. 

 Roots coming out thus, as, for example, 

 on the stem, are called adventitious. 

 Such roots are developed along the 

 stem of many climbing plants. Exam- 



j , ine and draw the roots of English ivy. 



See how many other common wild 

 climbers develop adventitious roots. 



Corn roots, showing prop roots devel- 

 oped at first node above grouad. 



