170 FOUNDATIONS OF BOTANY 
EXPERIMENT XXXV 
Occurrence of Starch in Nasturtium Leaves. — Toward the close of 
a very sunny day collect some bean leaves or leaves of nasturtium 
(Tropeolum). Boil these in water for a few minutes, to, kill the 
protoplasmic contents of the cells and to soften and swell the starch 
grains.! 
Soak the leaves, after boiling, in strong alcohol for a day or two, 
to dissolve out the chlorophyll, which would otherwise make it dif_fi- 
cult to see the blue color of the starch test, if any were obtained. 
Rinse out the alcohol with plenty of water 
and then place the leaves for ten or fifteen 
minutes in a solution of iodine, rinse off 
with water and note what portions of the 
leaf, if any, show the presence of starch. 
EXPERIMENT XXXVI 
Consumption of Starch in Nasturtium 
( Tropewolum) Leaves. — Select some healthy 
leaves of Tropzolum on a plant growing 
vigorously indoors or, still better, in the 
Fic. 123.— Leaf of Tropzo- : p 
lum partly covered with open air. Shut off the sunlight from 
Disks of Cork and ex- parts of the selected leaves (which are to 
ete ; ae 
a ad aa be left on the plant and as little injured 
as may be) by pinning circular disks of cork on opposite sides of 
the leaf, as shown in Fig. 123. On the afternoon of the next day 
remove these leaves from the plant and treat as described in the 
preceding experiment, taking especial pains to get rid of all the 
chlorophyll by changing the alcohol as many times as may be neces- 
sary. What does this experiment show in regard to the consump- 
tion of starch in the leaf? What has caused its disappearance? 
182. Rate at which Starch is manufactured. — The 
amount of starch made in a day by any given area of 
1 The leaves, collected as above described, may, after boiling, be kept in 
alcohol for winter use. They also make excellent material for the micro- 
scopical study of starch in the leaf. 
