6o2 



Journal of Agricultural Research 



Vol. XIII, No. II 



Table IV. — Relation of the amount of water transpired by corn and sorghttms to the 

 extent of the leaf surface of these plants — Continued. 



Period ending — 



T 1 '9' 



July 30: 



9 a. m 



II a. in 



I p. m 



3 P.m 



SP-m 



7P.m 



August 3: 



9 a. m 



II a. m 



I p. m 



3 p. m 



5 P- I'l 

 7P. m 



Ratio of- 



Dwarf Blackhull kafir 

 to Freed 's White 

 Dent corn. 



Leaf 

 surface. 



0.471 

 .471 

 .471 

 .471 

 .471 

 .471 



Loss of 



water per 



plant. 



0.477 

 •SOS 

 .566 

 .4X3 

 .406 

 .256 



Sherrod's T\Tiite Dent 



to Freed 's White 



Dent com. 



89 2 



Red Amber sorgo to 

 Freed 's White Dent 

 corn. 



Leaf 

 surface. 



o. i6i 

 .^6i 

 .261 

 .261 

 . 261 

 . 261 



Loss of 



wate per 



plant. 



D. 446 

 .529 

 •649 

 . 526 

 •438 

 .456 



Red Amber sorgo to 

 Freed's White Dent 

 com. 



0.283 

 .283 

 .283 

 .283 

 .283 

 • 283 



0.314 

 •475 

 •554 

 •504 

 •493 

 •394 



Fcterita to Freed's 

 White Dent corn. 



Leaf 

 surface. 



0.236 

 .236 

 .236 

 ■ 236 



• 236 



• 236 



Less of 



water per 



plant. 



0- 421 

 .368 

 •465 

 •356 

 . 276 

 .256 



Feterita to Freed's 

 White Dent corn. 



0.208 

 .20S 

 .208 

 .208 

 .208 

 .208 



183 



242 



314 

 258 



RATE OF TRANSPIRATION 



Since the loss of water from tlie different plants during a given period 

 is not proportional to the extent of their leaf surfaces, it follows that the 

 rate of transpiration per unit of leaf surface is not the same for each plant. 

 Both the Blackhull and the Dwarf Blackhull kafirs showed the lowset 

 transpiration rate per unit of leaf surface in all the experiments in v.-hich 

 these plants were used. The corn plant always showed the greatest loss 

 of water per plant, but in all the experiments, with the exception of those 

 in which kafir was used, it showed the lowest rate of water loss per unit of 

 leaf surface. The rate of transpiration per unit of leaf surface in any 

 given experiment was always higher for Dwarf milo Freed's sorgo, Red 

 Amber sorgo, and feterita than for any of the three varieties of corn 

 that were used. In many cases the rate of transpiration for these plants 

 was twice as high as that for corn under the same conditions. The rate 

 of transpiration of the different plants expressed in grams per square 

 meter of leaf surface per hour can be studied from the graphs in figures 

 I to 13. 



The foregoing discussion shows that the rate of transpiration per unit 

 of leaf surface was, with the exception of the two kafirs, higher for the 

 sorghums than for corn. This difference in transpiration rate became 

 more marked as the leaf surface of the corn plant increased over that of 

 the sorghums. At the earlier stages of growth, when the difference 

 between the extent of leaf surface of these plants was small, the rate of 



