PHYSIOLOGICAL PROCESSES IN PLANTS 73 



Corn Culture and Breeding: Thirteenth Report Kansas Board of 

 Agriculture, XVIII, 785-817. Bulletin 82, Illinois Agricultural Experi- 

 ment Station, 525-539. Hadley, Yearbook, Department of Agriculture, 

 1902. Harwood, World's Work, September, 1902. Shamel, Cosmo- 

 politan, May, 1903. 



PROBLEM XIV 



A study of the structure and work of roots. 



Materials. A number of bean, pea, and corn seedlings. * A 

 pocket garden. 



ROOT SYSTEMS 



Observation. Carefully wash the roots of the bean seed- 

 ling. Find a long main root (primary root) that is but a con- 

 tinuation of the lower stem. Find other roots (secondary roots) 

 that are branches of the primary root. Other small branches 

 (rootlets) may also be readily seen. Do the roots all take one 

 general direction ? 



Conclusions. 1. What reason can you give for the arrange- 

 ment of roots as you find them ? 



2. Why do roots not have such a definite shape as the stem ? 



a. Factors influencing Direction of Growth 

 1. EFFECT OF GRAVITY 



Note. The pulling force of the earth is known as the force 

 of gravity. 



Observation. Sprout some seeds in a pocket garden until 

 the roots are a half inch or so in length, then turn the 

 garden one fourth way around and examine again in a day 

 or so. Results? A growing plant in a pot may also be 

 inverted and the effect on the stem and roots noted. 



1 A pocket garden may be made as follows : Get a couple of 4 x 5 negative 

 plates, clean them, and cut 5 pieces of blotting paper about i inch smaller than 

 the glasses. Lay the blotters on one of the plates, and cut four s-inch strips of 

 wood so as to just fit on the glass outside the blotters. Moisten the blotters, 

 place some well-soaked seeds of mustard, barley, or radish on them, cover 

 the seeds with the other glass, and bind the glasses together with bicycle tape. 



