76 APPENDIX I. 
same level in the two arms. As root pressure is manifested, 
the mercury will rise in the long arm, and the actual amount 
of pressure may be deduced by calculation. 
EXPERIMENT 17. TO SHOW THE LIFTING POWER OF 
EVAPORATION. 
To the proximal end of the vigorous leafy shoot which was 
removed in Experiment 16 attach a glass tube fifteen or 
twenty inches in length, by means of a closely fitted piece 
of rubber tubing. Fill the tubing with water, and invert into 
a vessel of mercury. From time to time observe the rise of the 
mercury in the glass tube, and explain the strength of this pull. 
EXPERIMENT 18. TO SHOW CONDITIONS AFFECTING 
EVAPORATION. 
Prepare a leafy shoot as in Experiment 15 and continue the 
experiment until the water stands in drops on the leaves. 
This shows the effect of an atmosphere saturated with mois- 
ture or transpiration. Explain. 
After the drops have formed on the plant remove the bell 
jar and observe the gradual disappearance of the drops. 
Explain. How does variation of heat modify the results ? 
EXPERIMENT 19. TO SHOW HEAT PRODUCTION IN THE 
“GROWING SEED.” 
In (3) of Experiment 12 test with a thermometer the varia- 
tion of temperature in the bottle as compared with the outside 
air. 
III. GROWTH. 
EXPERIMENT 20. TO SHOW THE PLACE OF GROWTH. 
(a) In roots. 
Take a well-developed clean corn seedling, and place in a 
thistle tube so that the primary root passes down the tube. 
