232 Physiologie, 



ist auch der Fall, d. h. die Pflanzen sind schon 1—2 Stunden stark 

 nach Blau geneigt. Diese Methode eignet sehr zu Demonstrations- 

 zwecken, Daher sind beide Tropismen nicht identisch. 



Matouschek (Wien). 



Miller, E. C, Daily Variation of water and dry matter 

 in the leaves of corn and the sorghums. (Journ. agric. 

 Research, Washington. X. p. 11—46. 1917.) 



The writer summarizes the contents of his paper in these words: 



The Variation of water and dry matter in the leaves of corn 

 and the sorghums was determined by nine experiments in 1914, 

 two in 1915 and four in 1916. These experiments were conducted 

 with plants of Pride of Saline corn {Zea mays) ßlackhuli kafir 

 {Andropogon sorghum) and Dwarf milo [A. sorghum) which were 

 grown in the field, either in a series of plots or in alternate rows 

 on the same plot, Four of the experiments in 1914 extended only 

 through the daylight hours, but all the other experiments ranged 

 in length from 24 to 40 hours. In these experiments the water 

 and dry matter in the leaves were determined every two hours 

 during 22 days and 10 nights for corn and milo and during 18 

 days and 10 nights for kafir. 



The amount of water and dry mattter in the leaves of a given 

 variety of plant was obtained for any 2-hour period from 30 leaf 

 samples, each with an area of 1 Square centimeter, A Single leaf 

 on each of 30 representative plants furnished all the samples for 

 an experiment extending over any desired length of time. From 

 the results thus obtained, the amount of water and dry matter for 

 each Square meter of leaf, the percentage of water on a wet basis, 

 and the percentage of water on a dry basis were calculated. 



The amount of water in the leaves of milo was found to be 

 much lower at all times of the day and night than that of either 

 corn or kafir leaves at a like stage of development, while the 

 average water content of the corn and kafir leaves of corn, kafir 

 and milo averaged 118.5, 120.0 and 107.0 gm., respectively, for 

 each Square meter of leaf during the day periods and, taken in 

 the same order, 127.9, 132.7 and 115.5 gm. for the night periods. 

 The average Variation per square meter of leaf between the water 

 content of leaves during the day and night was 9.4 gm. for corn, 



12.7 gm, for kafir and 8.5 gm, for milo, The average Variation 

 between the maximum and minimum water content of the leaves 

 from 7 a. m. to 7 p.m. was 13.8, 8.4 and 7,8 gm, for each Square 

 meter of leaf respectively for corn, kafir and milo, while the 

 average ränge between the maximum watercontent of the leaves 

 during the night and the minimum amount during the day was 



23.8 gm. for corn, 25.9 gm. for kafir and 21.7 gm, for milo. 

 During the 22 days the evaporation as measured by a Living- 



ston porous-cup atmometer reached a maximum 18 times between 

 2 and 3 p. m, and 4 times between 3 and 5 p.m. In two-thirds of 

 the observations for corn and milo and in nine tenths of the obser- 

 vations for kafir the minimum water content of the leaves under 

 the conditions of these experiments occurred from two to four 

 hours earlier than did the maximum evaporation as measured by 

 the porous-cup atmometers. For the rest of the observations the 

 minimum amount of leaf water occurred at the time of maximum 

 evaporation. 



