AND TRANSPIRATION OF TREES 129 



structural changes in the leaves during successive periods of develop- 

 ment, maturity, and senility. 



Conclusions 

 From above results the following conclusions may be drawn: 



1) Daily maxima and minima values of water content occur at no 

 definite periods. 



2) Dailv results for transpiration, temperature, and relative humidi- 

 ty follow more or less definite courses. 



3) Water content is independent of the influences of transpiration, 

 temperature, and relative humidity. 



4) From 8 a. m. to 5 p. m. water content is constant. This is pro- 

 bably due to the fact that there was no scarcity in available soil-moisture. 



5) Average transpiration for the season was 1.21%, .83%, and .43% 

 for Fagus americana, Hamamelis virginiana, and Quercus alba respec- 

 tively. 



6) Rate of transpiration was highest during the early developing- 

 season, and lowest at time of leaf-fall. 



7) Average seasonal water content was 59.9%, 63.1%, and 59.2% 

 for Fagus americana, Hamamelis virginiana, and Quercus alba respec- 

 tively. 



8) Water content was highest during the early developing-season, 

 decreased gradually through May and early June, remained more or 

 less constant through middle and late June, decreased slightly through 

 July and August, and increased steadily from September 1st to leaf-fall. 



9) Seasonal variations in water content are probably due to seasonal 

 structural changes. 



Practical Applications 



Miinsch's^^ work has shown that the water content is a determining 

 factor in the appearance of fungous diseases in plants. While his work 

 dealt with the water content of the stem, it does not seem improbable 

 that the water content of certain leaves might sometime prove valuable 

 in determining conditions favorable or unfavorable for parasitic fun- 

 gous growths. 



VI. Summary 



The object of the present work was to determine seasonal variations 

 in water content and transpiration of leaves of Fagus americana, Ha- 

 mamelis virginiana, and Quercus alba. 



^^Miinsch, ' Untersuchungen uber Immunitat und Krankheitempfanglichkeit 

 der Hokpflanzen.' Naturwiss Zeitschr. f. Forst. u. Landw. 1909. 7:54-75, 87- 

 114, 129-160. 



