62 LABORATORY AND EIELD EXERCISES 



a. Note and record temperature, general light intensity, 

 and relative humidity at the time of taking each 

 reading. Take records at convenient intervals for 

 about three days. 



I. Write up the experiment as usual. Under Results tabu- 

 late your readings to show temperatures, light inten- 

 sity, and relative humidity, as well as the amounts 

 of water lost at stated periods and for the entire period. 

 c. Summarize the main factors which have apparently 

 caused variations in the rate of transpiration in your 

 experiment at different periods. 



2. Record the loss of water by transpiration from a potted 

 plant, as for the previous experiment, and record results 

 as explained above. Class experiment. 



WATER ASCENT 



1. The path and rate of water ascent. Individual experiment. 

 Cut off leafy herbaceous shoots or stalks of celery under 

 water and add eosin to make a strong colored solution, 

 and observe as follows : 



a. Hate of water ascent. If transparent stems of Impatient 

 or bleached stalks of celery are vised, the progress of 

 the colored solution may be observed in the stem or 

 in the leaf veins. 



(1) After from three to five minutes remove the stem 



from eosin and make cross cuts of it, beginning 

 at the apex, until the coloration by eosin appears 

 in the cross section. Measure the length of the 

 stem traversed by the- solution during the time 

 it was left in eosin. 



(2) From the above data determine the rate of ascent 



per hour. Compare with the rates of water ascent 



