i EXPERIMENTAL PLANT PHYSIOLOGY 



otherwise air also will be prevented from reaching the 

 roots. The third plant is left unwatered. 



Observations. — The first seedling thrives. The 

 second and third die. 



Inference. — The life of a plant cannot be maintained 

 unless water is supplied to the roots. Thus : The root 

 is the absorbing organ of the plant. 



{Note.—This experiment applies only to land plants ; 

 in submerged aquatic plants absorption takes place 

 over the entire surface. It must also be remembered 

 that a cut stem is able to absorb.) 



Experiment 3 



Aim. — To determine the rate 



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Fig. 1 1 



at which a plant is 

 absorbing water and 

 the external condi- 

 tions by which the 

 rate is affected. 



Method.— The 

 pieces of apparatus 

 needed in this ex- 

 periment are a glass 

 flask or gas-jar with 

 cork to fit, a thistle- 

 funnel with a tap, a 

 piece of very narrow 

 glass-tubing, a ther- 

 mometer, and a 

 well - grown potted 

 plant with a woody 

 stem that will not 

 easily be injured. 



The glass-tubing 

 is bent at right 



angles so that the long arm measures at least 15 inches. 

 The length is marked off in inches by means of strips 

 of gummed paper or a cardboard scale. 



The thistle-funnel, the glass-tubing and the plant 

 are then fitted into the cork. 



