Mar. 8,1924 Carbohydrate Variations in Corn and Sorghum Leaves 803 
THE CARBOHYDRATES OF THE LEAVES 
THE TOTAL SUGARS 
The total sugars in the leaves of com and the sorghums begin to 
increase between 4 and 6 a. m. and reach a maximum which varied in 
these experiments from 12 m. to 5 p. m. After the maximum was reached 
the sugar disappeared rapidly until 9 to 10 p. m., after which the decrease 
was very gradual until daylight again appeared. In five of the ten 
observations the maximum amount of sugar in the leaves occurred at 
the same time as the maximum amount of dry matter, while in the other 
five cases the maximum amount of sugar was reached at periods varying 
from one to six hours earlier than the maximum amount of dry matter 
in the leaves. There is no evidence from these experiments to show 
that there is any difference between the corn and sorghum in regard to 
the time of day at which the maximum amount of sugar and the maxi¬ 
mum amount of dry matter may occur in the leaves. The fact that in 
some experiments the maximum amount of sugar in the leaves occurred 
earlier in the day than the maximum amount of dry matter shows that 
in these cases the increase in the dry weight of the leaves was due in 
part to the temporary storage of materials other than the sugars. 
In the three comparative experiments with Pride of Saline com and 
Dwarf Yellow milo, the maximum percentage of sugar in the leaves 
was respectively 6.03, 6.33, and 6.44 for the com and 8.27, 6.68, and 
7.49 for the milo. The average maximum amount of sugar in the leaves 
of the milo was thus about 1 per cent higher than in the leaves of corn. 
The maximum sugar content of the leaves during the day, expressed in 
grams per square meter of leaf, amounted to 2.94, 3.25, and 3.37 for 
corn and 4.34, 4.11, and 3.83 for milo, respectively, in each of the three 
successive experiments. The maximum increase in the amount of 
sugar in the leaves during the day was respectively 1.73, 2.50, and 1.86 
gm. per square meter of leaf for the com and 2.63, 2.90, and 1.92 gm. 
per square meter of leaf for the milo. A comparative experiment was' 
conducted with Dwarf Yellow milo and Red Amber sorgo on July 17 and 
18, 1919, but no significant differences were observed in regard to the 
behavior of the total sugars in these plants. Table X gives a summary 
of the more important facts concerning the changes in sugars of the 
leaves during the day. 
THE INSOLUBLE CARBOHYDRATES 
In the experiment of July 25 and 26, 1917, the maximum amount of 
insoluble carbohydrates per square meter of leaf was reached at 6 p. m. 
in both the com and milo, while the maximum sugar content occurred at 
2 p. m. In the experiment with Dwarf milo on August 3, 1917, the 
maximum amount of sugar per square meter of leaf was reached at 12 m., 
but the maximum' amount of insoluble carbohydrates did not occur until 
8 p. m. In the observation on com during the experiment of July 3 and 
4, 1919, the maximum amount of sugar and insoluble carbohydrates per 
square meter of leaf was reached at 5 p. m. After the insoluble carbo¬ 
hydrates reached a maximum in the leaves, they showed little or no 
diminution in amount until about midnight, when they decreased rapidly 
until daylight. 
