492 



ANNUAL. REPORT SMITHSONIAN INSTITUTION, 19 3 8 



the ceiling of the room, so the apparatus was carefully moved to a 

 nearby laboratory which had a stairway in it, and the bulb was carried 

 into the room above. Unfortunately, a period of adjustment was not 

 allowed, as should have been done, so that when, under 3 atmospheres 

 pressure, the column began to fall, no definite cause could be assigned 



I830r 



„-i^-Apparatus move J 

 3 aim. 



2 otrr. 



Figure 2.— A curve showing the eSect of imposing pressures up to 3 atm. against the secretion pressures 

 developed by a single tomato root. 



for the drop. But the fact that when the pressure was reduced again 

 to 2 atm., the column did not resume the upward course it had pre- 

 viously held at that pressure, indicated that a leak in the apparatus 

 had probably been brought about in moving. The important fact 

 demonstrated by this experiment is that a pressure of 2 atm. was not 

 sufficient to retard noticeably secretion of water from the uninjured 

 base of a single root of tomato. 



