ELISHA MITCHKLL SCIENTIFIC SOCIETY. 65 



major were choisen because they transpire water rapidly and in large 

 amounts, and hence any change would be more aptjarent. 



The relative transpiration of moistened and dry leaves was tested 

 by fastening leaves with wax in test-tubes filled with water, and 

 allowing the evaporation to go on during several days. The stems 

 dipped equal distances beneath the surface of the water and the 

 leaves to be kept moist, were in some cases wetted with a sponge, in 

 others by the spray from a wash bottle. The leaves were placed in 

 the diffuse light of the laboratory and inequalities in the exposure 

 to the light neutralized by interchanging the position of the tubes. 

 Various leaves were experimented upon — maple, grape, geranium, 

 convolvulus major, and in all cases, at the end of three or four days, 

 the transpiration and consequent loss of water in the tubes had gone 

 nearly twice as far where the leaves were dry as where they were 

 wet. Of course these leaves were not wet all the time. They were 

 kept continuously wet during a greater portion of the day, but dried 

 off at night. Yet even this greatly retarded the evaporation, a 

 result directly contrary to Wiessner. Again, to test this transpira- 

 tion, lejives of the geranium and of the zinnia were weighed and 

 then allowed to lie, the one on paper and the other on glass with 

 occasional wettings. These last were dried between filter paper 

 before reweighing. This would show the difference of transpiration 

 by the loss of the original water of the leaf. The results were as 

 follows: 



Loss. Wet Leaves. Dry Leaves. 



L After 6 hours 6.6 per cent. 9.0 per cent. 



" 24 " 13.7 " 14.5 " 



" 30 '• 15.5 16.0 



II. " 24 " 366 39.8 



As to flowers transpiring more slowly than leaves, and hence cut 

 flowers with leaves wilting more rapidly than those without, Wiess- 

 ner's term, "most flowers," is indefinite. I have tried geraniums, 

 zinnias and convolvulus. 



The weights in the other cases show the relative loss of water : 

 Loss. Flowers, Leaves. 



I. After 6 hours 10.6 per cent. 9,0 per cent. 



" 24 " 24.8 " 14.5 



30 " 28.4 " t6.o 



II. Flowers and leaves. Leaves. 



24 " 29. 3 per cent. 28. 9 per cent. 



26 " 30.8 " 30.5 " 



" 30 " 33.9 " 33-8 



" 48 " - --50.3 " 49.8 



