EXERCISE 16. EARLY GROWTH OF THE CORN PLANT 



Equipment : Preparation for this exercise must be made 

 four weeks in advance, by planting two small plots of corn, 

 one at the depth of one inch and the other three inches deep. 

 Repeat this planting each week, in order to have, for the 

 exercise, plants one week old and others that have reached 

 the ages of two, three and four weeks. The plantings may 

 be made in soil, but the plants will be much more eaisily 

 handled if grown in boxes of sand, since the sand will wash 

 off the roots much more readily than soil. 



Method: Dig up a sufficient number of plants and care- 

 fully wash the sand away without injuring the roots. Ex- 

 amine the root systems of the plants of different ages and 

 compare those planted at different depths. Make draw- 

 ings of the entire plants at different stages of their develop- 

 ment and show the three temporary roots which develop 

 first and also the permanent roots which make their appear- 

 ance later at one of the joints or nodes situated about one 

 inch below the soil surface. 



Discussion: The roots of the corn plant may be divided 

 into three groups: (1) temporary, (2) permanent feeding 

 roots, and (3) brace roots. When the kernel of corn germi- 

 nates, it sends down into the soil a shoot from which two or 

 three lateral branch roots develop. These roots with their 

 l)ranches form the temporary root system and supply the 



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