July 2,1917 Variation of Water in Leaves of Corn and Sorghums 39 



the next two hours it increased 6.7 gm., then decreased 2.2 gm. until ii 

 p. m., when the amount of dry matter remained constant until i a. m., 

 after which a gradual depletion began to occur. (See Table III, Aug. lo- 

 26, 1914, and fig. 3, 4, and 5.) 



II. PERCENTAGE OF DRY MATTER 



The average percentage of dry matter in the leaves during both the 

 day and night was found to be 28.7 for corn, 30.1 for kafir, and 34.3 for 

 milo. The average percentage of dry matter in the leaves during the 

 day periods was 29.0, 30.5, and 34.7, respectively, for com, kafir, and 

 milo, while taken in the same order the average percentage of dry matter 

 during the 10 night periods was 28.3, 29.8, and 33.9. This made an 

 average difference in the percentage of dry matter between the day and 

 night of approximately 0.7 for all three plants. With but few excep- 

 tions the maximum percentage of dry matter in the leaves of all three 

 plants occurred between 11 a. m. and 3 p. m. The average difference 

 between the maximum and minimum percentage of dry matter during 

 the day was 3.5 for corn, 3.3 for kafir, and 4.6 for milo. The minimum 

 percentage of dry matter in the leaves of com during the night occurred 

 twice at i a. m., 3 times at 3 a. m., and 5 times at 5 a. m. In all the 

 10 night experiments with milo the minimum percentage of dry matter 

 occurred at 5 a. m. In 8 night experiments with kafir the minimum 

 percentage of dry matter was in 2 cases at i a. m. and in 6 cases at 5 

 a. m. The average difference between the maximum and minimum per- 

 centage of dry matter during the night was 3.0, 4.2, and 4.8 for com, 

 kafir, and milo, respectively. The average difference between the maxi- 

 mum percentage of dry matter during the day and the minimum per- 

 centage during the night was 5.1 for corn, 5.9 for kafir, and 6.0 for milo. 



For the purpose of comparison, the results have been obtained by 

 other investigators in their study of the daily variation of the water 

 content of leaves are briefly reviewed here. Lloyd ^ found that the per- 

 centage of water on a dry basis in the leaves of Fouquieria splendens 

 varied from 225 to 300 as extreme limits between day and night and 

 that the diminution of water in the leaves began at daybreak and con- 

 tinued until some time between noon and 4 p. m. After that time the 

 water in the leaves increased till approximately 4 a. m. In experiments 

 with the cotton plant, Lloyd ^ found that the leaf water stated in per- 

 centage of dry weight varied under usual conditions between 318 and 

 220 per cent and that the minimum leaf water content was reached at 

 2 p. m. or thereabouts. The amount of loss of leaf water when thus 

 determined was from 7 to 15 per cent of the initial amount at sunrise. 



' LtOYD, F. E. THE RELATION OP TRANSPIRATION AND STOMATAI, MOVEMENTS TO THE WATER CON- 

 TENT OP THE LEAVES IN FOUQUIERIA SPLENDENS. In Plant World, V. 15, no. i, p. 1-14, i fig. 1912. 



2 . LEAF WATER AND STOMATAL MOVEMENT IN GOSSYPIUM AND A METHOD OP DIRECT VTSUAI, 



OBSERVATION OP STOMATA IN SITU. In Bul. Torrey Bot. Club, v. 40, no. i, p. 1-26, 3 fig. 1913. 



