POTOMETER 



for demonstrating the effect on transpiration 

 of varying external conditions 



The rate of transpiration is indicated by a bubble in the graduated tube, 

 the bubble moving forward as the plant absorbs water. 



Opening the stop-cock sends the bubble back to its starting point, again 

 ready for use. 



For comparative records, one takes the distance traversed by the bubble 

 in a given time, or the time it requires to travel a given distance. 



This instrument, like all of those designed by Professor Ganong, is cor- 

 rect in principle and simple in operation. 



Our Catalog of Ganong Botanical Apparatus contains much authoritative 

 information. It describes at length 26 different pieces of appa- 

 ratus for use in Plant Physiology. It is free on request. 



Bausch £5 Ipmb Optical (5. 



HCW YORK WASHINGTON CHICAGO SAN FRANCISCO 



london F10CHESTEH,N.Y. ™ankfort 



Leading American Makers of Microscopes, Projection Apparatus (Balopticons), 

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