THE STEM 
113 
ExprriMEnt 59. WHAT BECOMES OF THE WATER THAT GOES INTO THE 
LEAVES ? — Cover the top of the vessel containing the leafy twig used in the 
last experiment with a piece of card- 
board, having first cut a slit in one side, 
as shown in Fig. 128, so that it can be 
slid into place without injuring the 
stem. Invert over the twig a tumbler 
that has first been thoroughly dried, 
and leave in a warm, dry place. After 
an hour or two, what do you see on the 
inside of the tumbler? Where did the 
moisture come from? 
EXPERIMENT 60. THROUGH WHAT 
PART OF THE STEM DOES THE SAP FLOW 
UPWARD ? — Remove a ring of the cor- 
Fie. 129.—A 
twig which had been 
kept standing in 
water after the re- 
moval of a ring of 
cortical tissue: a, 
level of the water; 
b, swelling formed at 
the upper denuda- 
tion; c, roots. 
tical layer from a 
twig of any readily 
rooting dicoty], 
such as_ willow, 
being careful to 
leave the woody 
part, with the cambium, intact. Place the end below 
the cut ring in water, as shown in Fig. 129. The leaves 
above the girdle will remain fresh. How is the water 
carried to them? How does this agree with the 
movement of red ink observed in 115 and 122? 
Fic. 128. — Experiment showing 
that moisture is thrown off by the 
leaves of plants. 
EXPERIMENT 61. THROUGH WHAT PART DOES THE 
SAP COME DOWN ? — Next prune away the leaves and 
protect the girdled surface with tin foil, or insert it 
below the neck of a deep bottle to prevent evaporation, 
and wait until roots develop. Do they come more 
abundantly from above or below the decorticated 
ring? 
124. The three principal functions of the 
stem are:— (1) to serve as a mechanical sup- 
port and framework for binding the other 
organs together and bringing them into the best attainable 
relations with light and air; (2) as a water carrier, or pipe 
line, for conveying the sap from the roots to the parts where 
it is needed; and (3) as a receptacle for the storage of foods. 
