AND TRANSPIRATION OF TREES US 



Conclusions 



From above results the following conclusions may be drawn: 



1. Average water content for Populus tremuloides is 61.8%. 



2. Average water content for Populus grandidentata is 59.6%. 



v3. There is no definite period for maxima and minima water content. 



4. With fluctuations, there is a general increase in water content 

 by night, and a general decrease by day. 



5. Under like conditions curves for both species follow each other 

 more or less closely, indicating a common influential factor. 



6. Water content is independent of both temperature and relative 

 humidity. 



7. Under like atmospheric conditions, for both species, water 

 content under hydrophytic is greater than under xerophytic 

 conditions. 



8. With the exception of xerophytic cloudy results, where day 

 readings only were obtained, Populus tremuloides water content 

 was greater than that for Populus grandidentata. 



9. With the exception of Populus tremuloides under xerophytic 

 situations by day, water content for cloudy conditions was 

 greater than that for clear. 



10. By night for both species, water content for hydrophytic clear 

 was greater than for hydrophytic cloudy conditions. 



11. Irregularities are prominent in Populus tremuloides under xero- 

 phytic conditions. 



V. The Present Problem 

 Location and Ecological Conditions 



While the main part of the problem at hand was to determine the 

 water content in leaves of Fagus americana, Hamamelis virginiana, 

 and Quercus alba during the seasonal changes, parallel experiments 

 regarding the amount of transpiration for these leaves were run simul- 

 taneously. 



The work was done on a Brandywine farm located 6 miles southwest 

 of West Chester, Pa., and 30 miles west of Philadelphia. The experi- 

 mental field was confined to the northwest corner of a twenty acre 

 woodlot, whose timber had been removed for the first time, 25 years 

 ago in lumbering processes. Here is now a splendid second growth of 

 hardwoods with a few towering relics of the original stand. 



The plot selected for the experimental work was irregular in outline: 

 its northern boundary line was a twelve foot cart-road leading into the 



