May 29, 1916 Root Systems and Leaf Areas of Corn and Sorghum 321 



NUMBER OF SECONDARY ROOTS 



It has been shown in the foregoing discussion of the isolation of the 

 root systems of com, BlackhuU kafir, and Dwarf milo at the various 

 periods of grov/th, that no marked differences were to be observed 

 between these plants in regard to the number and general extent of their 

 primary roots. It was thought advisable on this account to make a 

 study of the number of secondary roots possessed by the three plants 

 at different stages of growth. 



After the isolated root systems had been studied and photographed 

 the primary roots of each plant were cut into inch lengths and the number 

 of the secondary roots originating from each unit of length was deter- 

 mined under a dissecting microscope. The results of this investiga- 

 tion for all the stages of root growth examined in 191 4 and 191 5 are 

 shown in Table V. It was found from 321 observations of the roots of 

 the corn, 311 of Dwarf milo and 210 of BlackhuU kafir that the number 

 of secondary roots per unit of length of primary root was approximately 

 twice as great for the two sorghums as for the com. This fact stands 

 out strikingly not only for each year but for all the different stages 

 of the development of the root systems (PI. XLII, fig. 1,2). 



Table V. — Number of secondary roots per unit of length of primary roots of corn, kafir, 

 and milo in IQ14 and IQIS at Garden City, Kans. 



WEIGHT OF THE ROOTS AND AERIAL PORTIONS OF THE PLANTS 



A comparative study was made of the dry weight of the aerial parts 

 and roots of corn, BlackhuU kafir, and Dwarf milo in 191 4, and for these 

 three plants and Dwarf BlackhuU kafir in 1915. The root systems that 



