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ECOLOGY OF TILIA AMERICANA 



I. COMPARATIVE STUDIES OF THE FOLIAR TRANSPIRING 



POWER 



CONTRIBUTIONS FROM THE HULL BOTANICAL LABORATORY 253 



James E. Cribbs 

 (WITH THIRTEEN FIGURES) 



Introduction 



Up to the present time transpiration studies have been con- 

 ducted almost exclusively with potted plants, or upon plants 

 which were growing under controlled conditions. This is due to 

 the fact that most of the investigation has been purely physio- 

 logical in its aims; and since the factors influencing this process 

 are numerous, they can evidently be more definitely calculated 

 in controlled habitats than in natural ones. 



It has been the investigator's aim to carry this line of 

 experimentation into the field, in an endeavor to determine what 

 differences occur in the relative foliar transpiring power of a cer- 

 tain species when growing in different environments. It was at 

 once recognized that the complication of factors which influence 

 transpiration is considerably increased, and the precision with 

 which they may be measured and the relative values to be attrib- 

 uted to each are perhaps less exact than when such investigation 

 is made under greenhouse or laboratory conditions. Nevertheless, 

 there are certain problems which of necessity must be worked out 

 under field conditions, especially when we wish to determine the 

 ecological value or relationship of the environment. 



For this investigation Tilia americana was chosen because it, 

 perhaps more than any other of our tree species, grows under a 

 wide range of environmental conditions. This is especially true 

 when we consider its unusual ability (as a member of a mesophytic 

 forest) to surmount moving dunes which chance to advance upon 

 it. This ability of Tilia to persist on the moving sands brings it 

 Botanical Gazette, vol. 68] [262 



