Does it rise from the first ?

Another method is to attach a tube bent in the shape of a
modified S, with the free arm of considerable length, to the
cut-off stump of a plant. Pill the tube by first pouring in a
little water and then mercury, so that the latter stands at the



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 varior
tion of temperature in the bottle as compared with the outside
air.
ni. GROWTH.
EXPERIMENT 20. TO SHOW THE PLACE OF GROWTH.
(a) In roots.
