The Boot and the Soil. 77 



less in extent than the branches. It appears from the 

 observations recorded that even in such plants as the 

 melon and squash, the horizontal extent of the roots 

 usually equals or exceeds that of the runners. As the 

 diffusion of soluble matters in the soil water is probably 

 much hindered by the soil particles, the roots of plants 

 need to travel farther after food than do the branches, 

 which develop in a freely circulating medium. Espe- 

 cially is this true of plants growing in poor soil. 



109. The Depth of Roots in the Soil. It appears 

 from the observations recorded that the extreme depth 

 reached by roots is generally less than their greatest 

 horizontal extent. The distance reached by the deeper 

 roots is probably governed largely by the nature of the 

 sub-soil and the depth of free ground water. But in 

 most annual crops a comparatively small part of the 

 root system develops below the plow line. At the 

 Geneva Experiment Station* the chief root-feeding 

 ground of the field and garden crops grown in that 

 locality appeared to be from three to ten inches below 

 the surface, while that of crops making large develop- 

 ment of stem and foliage during summer, as Indian 

 com, sorghum, tobacco and the Cucurbits, appeared to 

 be shallower than in slower-growing crops. 



A portion 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 

 directions. At the Geneva Experiment Station, numer- 

 ous roots of sweet corn were found within an inch of 



* See Report of New York Agricultural Experiment Station, 1886, 

 p. 165. 



