70 



PRINCIPLES OF PLANT CULTURE 



ten inches below the surface, while that of crops making 

 large development of stem and foliage during summer, 

 as Indian corn, sorghum, tobacco and the Cucurbitae, 

 appeared to be shallower than in slower-growing crops. 



A part of the roots of many crops grow very near the 

 surface of the ground. Branches from the main horizontal 



roots often grow upward 

 as well as in other direc- 

 tions. At the Geneva 

 Experiment Station, nu- 

 merous roots of sweet 

 corn were found within 

 an inch of the surface, 

 and in a tall-growing 

 southern corn, roots of 

 considerable size started 

 at a depth of only half an 

 inch. The main root of a 

 Hubbard squash vine was 

 traced a distance of ten 

 feet, in which its depth 

 varied from two to five 

 inches. In tobacco fields, 

 the rootlets sometimes 

 literally protrude from 



.ab^eS:n;:oS! '"'"'"' ^^' '"^'^^'^ ^^ t^e Soil in 



warm, wet weather (231). 

 110. The rate of root growth in rapidly developing 

 plants is often extremely fast. President Clark, formerly 

 of the Massachusetts Agricultural College, concluded 

 from very careful examinations and measurements of the 

 roots of a squash vine grown under glass, that rootlets 

 must have been produced at the rate of at least one thou- 



Fio. 33. 



