426 



REPORT OF THE COMMISSIONERS OF 



short grass for a period of eight years was 30. 1 inches, while for long grass for a 

 period of eight years the mean evaporation is given at 44.0 inches. Inasmuch as 

 these interesting tabulations may be readily referred to in Beardmore's Hydrology, 

 they are not reproduced here. 



TRANSPIRATION OF PLANTS. 



This division of the subject, while discussed extensively by the great botanical 

 writers, Von Sachs, Kerner and Oliver, and others, has not as yet been reduced by the 

 botanist to numerical relations. The best general discussion of the how and why 

 plants transpire water, may be found in Kerner and Oliver's Natural History of Plants, 

 where every phase of the question has been touched upon. Reference may also be 

 made to Von Sach's Physiology of Plants, and Bessey's Botany, where various facts 

 relating to the general subject and statements of experiments are given. Bulletin No. 

 7, Forestry Division of the United States Department of Agriculture — Forest 

 Influences — may also be consulted. Among other interesting data there given, we 

 may refer to Wollny's experiments on water transpiration of agricultural crops, which 

 are of special interest, not only because they are recent determinations, but because of 

 verifying the work of Risler and others. They are as follows: 













DAILY 



CROP 



GROWING PERIOD 



TOTAL WATER. 

 INCHES 



CONSUMPTION" 



OF WATER. 



INCHES 



Winter rye, .... 



April 20 to August 13, 1879, 



II.44 



O.IO9 



Summer rye, . . . . 



April 20 to August 14, 1880, 



'13-25 



0.1 14 



Barley, ..... 



April 20 to August 3, 1879, 



I2.00 



0.1 14 



Peas, ..... 



April 20 to August 3, 1879, 



13.88 



O.I32 



Oats, ..... 



April 20 to September 14, 1880, 



15.12 



O.IO3 



Beans, ..... 



April 10 to September 10, 1880, 



13.80 



O.O96 



Red clover (first season) 



April 20 to October 1, 1879, 



!3-5 6 



O.083 



Red clover (second season), 



April 20 to October 1, 1880, 



17-95 



O. IO9 



The following figures of water consumption of certain plants for the growing 

 season, computed from the data of Hales, Schleiden, Schiibler and Hohnel, and others, 

 are also mostly derived from Bulletin No. 7 on Forest Influences, certain apparently 

 incongruous data there given being omitted: 



