LABORATORY AND FIELD WORK 415 



17. Make a list of the uses to which the different parts of the 

 corn plant are put kernels, cobs, husks, stems, and leaves. 



18. Why is so large a part of the world's corn crop produced in 

 the United States ? Which states in the ' United States produce 

 the most corn ? Why are these states best suited to corn growing ? 



19. Further suggestions for practical study may be found in 

 Farmers' Bulletins 409 and 617, published by the United States 

 Department of Agriculture. 



CHAPTER XIV 



1. Study the root systems of as many as possible of the follow- 

 ing : dandelion, clover, sweet potato, radish, beet, dahlia, some of 

 the grasses or grains, and some small trees and shrubs. Which 

 of those studied have large primary roots? Which have branch- 

 ing primary roots? Which have clustered roots? Which have 

 fibrous roots? 



2. With a hand lens examine cross sections of roots of corn, of pea, 

 and of some woody plant. Find the epidermis, cortex, vascular 

 bundles, and pith. How does the arrangement of these tissues 

 compare with their arrangement in the stems that you have studied ? 

 Sketch a section. Look for the beginnings of secondary roots. 

 Where do they start? 



3. Study the roots of an onion or other plant growing in water. 

 Notice the cap-like mass of cells (root cap) covering the tip of the 

 root. What is the function of the root cap ? 



4. Study a prepared longitudinal section of a root tip under 

 the compound microscope. Can you recognize the root cap? 

 The region of embryonic cells? How do the cells in the older 

 parts of the section differ from the embryonic cells ? 



5. Mark with India ink an actively growing bean root, prefer- 

 ably one not more than two inches long, at intervals of one-fourth 

 inch. Place the plant in a moist chamber and examine it from 

 day to day. In what part does most of the growth in length take 

 place ? 



6. By means of pins, fasten bean seedlings with roots about an 

 inch in length to a block of wood so that the roots point in various 

 directions. Place the block in a moist chamber and observe the 

 seedlings after twenty-four hours. In which direction do the roots 



