140 Kansas Academy of Science. 



stage of development. The average dry weight of a square meter of 

 leaf for all the observations made was 48 gms. for com, 53 gms. for 

 kafir and 56 gms. for milo. The average difference between the mini- 

 mum and maximum amount of dry matter in the leaves for each square 

 meter of leaf from 7 a. m. to 7 p. m. was 4.5 and 8.0 gms., respectively, 

 for corn, kafir and milo. The increase in dry matter began at daybreak, 

 and the maximum amount of dry matter in the leaves occurred in most 

 cases between 2 and 5 p. m. The rate of increase of the dry matter in 

 the leaves during the portion of the day when the climatic conditions 

 were severe was much higher for milo than for either corn or kafir. 



COMPARATIVE TRANSPIRATION. 



Five experiments were conducted in 1916 and eight in 1917 to de- 

 termine the relative transpirations of corn and the sorghums. Pride 

 of Saline corn, Blackhull kafir. Dwarf Blackhull kafir and Dwarf milo 

 were used in 1916, and in 1917, in addition to these, Freed's White Dent 

 corn, Sherrod's White Dent corn, Freed's sorgo. Red Amber sorgo and 

 feterita were used. The plants were grown in large galvanized iron 

 cans with a capacity of about 120 kilos of soil. The soil used in 1916 

 had a water content of 18 per cent and a wilting coefficient of 11.1, 

 while the moisture content of the soil used in 1917 was 22 per cent and 

 had a wilting coefficient of 15.1. 



The transpiration was determined in most of the experiments every 

 two hours from 7 a. m. to 7 p. m. Each experiment extended through two 

 or three days. In 1916 the cans were placed in the open on the surface 

 of the ground, but in 1917 they were placed in a pit in the center of a plot 

 that was planted to corn. The pit was of such a depth that the top of 

 the cans were on a level with the surface of the ground. 



Blackhull kafir and Dwarf Blackhull kafir always had the lowest rate 

 of transpiration per unit of leaf surface in the experiments in which 

 these plants were used. All the varieties of corn used always trans- 

 pired more water per plant during any given period than did any of 

 the sorghums. Their rate of transpiration per unit of leaf surface was, 

 with the exception of the kafirs, always lower than that of the sorghums. 

 The rate of transpiration per unit of leaf surface for feterita. Dwarf 

 milo, Freed's sorgo and Red Amber sorgo was much higher than that 

 of the corn plant under the same conditions. The difference in the 

 transpiration rate of corn and the sorghums was more marked when the 

 plants had reached their full leaf development and the difference in 

 leaf surface of these plants had reached a maximum. The difference in 

 the transpiration rate per unit of leaf surface was always more evi- 

 dent under severe climatic conditions than under conditions where the 

 evaporation was low. 



SUMMARY. 

 In comparing the corn and sorghum plants, it will be seen that in 

 all stages of their growth the sorghum plants have a primary root 

 system that is just as extensive as that of the corn plant. In addition, 

 the sorghums possess twice as many secondary roots as the corn at any 

 stage of its growth. The leaf area of the corn plant at all stages of its 

 growth is approximately twice as great as that of the sorghums. 



