78 



Principles of Plant Culture. 



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 the surface of the soil 

 in waiin, wet weather (231). 



110. The Eate of Root Growth in rapidly develop- 

 ing plants is often extremely fast. President Clark, 



formerly of the Massa- 

 chusetts Agricultural 

 College, concluded from 

 very careful examina- 

 tions 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 

 thousand feet per day 

 during the latter part 

 of the growth period. 



111. Relation of 

 Roots to Food Supply. 



In the extent of ground 

 occupied, root growth is 

 relatively less in moist 

 and fertile soils than in poorer and drier ones, but the 

 roots are proportionately more branched. In wet 

 seasons, a given plant has less extensive root develop- 



FiG, 33. Young clover plant show- 

 ing tubercles on roots (t). (From 

 nature.) 



