AGRICULTURAI. BOTAXY, CHEMISTRY AND PHYSIOLOGY OF PLANTS 160I 



to slag varied in the first place with the size of the dressing and the solu- 

 bility of the manganese, and to a less extent, with the nature of the soil 

 and its manganese content. 



Further experiments are recommended in order to decide whether 

 heaw dressings of manganese slag may be employed with profit by farmers. 



1 1 70 - Comparative Study of the Root Systems and Leaf Areas of Corn and the Sor- 

 ghums. — ^MillerE- C.in Journal of Aayicultiiral Research, Vol. VI, No. 9, pp. 311-331. 

 Washington, May 29th 1916. 



During the summers of 1914 and 1915 a series of investigations was 

 conducted to determine the fundamental characteristics possessed by the 

 sorghum plants (Andropogon sorghum) which enable them to withstand 

 severe climatic conditions better than the corn plant {Zea Mays). The 

 present paper deals with the comparative study of the root systems and 

 leaf areas of corn and of the sorghums Blackhull Kafir and Dwarf IVIilo. 

 These experiments were carried on at the State Branch Experiment Station 

 at Garden City, Kansas, in latitude ^y^ 58' north and longitude 100° 55' 

 west (Greenwich) and at an altitude of 2940 feet. 



The root systems of Pride of Sahne corn, Blackhull Kafir and Dwarf 

 Milo sorghum plants which were grown in alternate rows, were isolated 

 in the field at four stages of growth in 1914 and at three stages of growth 

 in 1915. All told, the root systems of 33 plants were isolated and studied. 

 It was found that for a given stage of growth each plant possessed the 

 same number of primary roots and that the general extent of these roots 

 in both a horizontal and vertical direction was the same for all three plants. 

 The maximum depth of root penetration for mature Dwarf Milo, Black- 

 hull Kafir, and corn was found to be 6 feet for both the years 1914 and 

 1915. Blackhull Kafir and Dwarf Milo possessed approximately twice 

 as many secondary roots per unit of primary root as did the corn plant. 

 This is true not only for both years but also for all stages of the root sys- 

 tems examined. Both primar^^ and secondary roots of the sorghums 

 were found to be more fibrous than those of the corn plant. 



The relation of the weight of the dry matter of the aerial portions of 

 mature plants to the weight of the roots was determined in 1914 for 36 

 Dwarf Milo plants, 30 Blackhull Kafir plants and 12 corn plants. In 1915 

 the same determinations were made for 24 Dwarf Milo, 14 Dwarf Black- 

 hull Kafir, 23 Blackhull Kafir and 24 corn plants. 



The average ratio of the dry weight of the grain, stem and leaves 

 of standard Kafir to the dry weight of the roots was found to be 15 and 

 14.9 for the years 1914 and 1915 respectively, while the dry weight of the 

 stem and leaves of the same plant was on the average 10.9 times that of 

 the root weight in 1914 and 10. i times the root weight in 1915. For 

 Dwarf Milo the corresponding figures were 15.7 and 15 ; 9.6 and 8 respec- 

 tively. For corn the weight of the stem and leaves was 9.6 times the root 

 weight in 1914 and 7,8 times in 1915. For Dwarf Blackhull Kafir in 1915 

 the figures were 15.7 with the grain and 8.9 without the grain. 

 The results of the experiments in regard to the soil-moisture content and 

 depth of root penetration seem to show that under the conditions of the 



AGRICULTURAL 



BOTANY. 



CHEMISTRY 



AND 

 PHYSIOLOGY 

 OF PLANTS 



