THE LIVING PLANT FORMS STARCH 113 
are almost entirely white, the chlorophyll having been 
removed. We will rinse them a moment in water and 
then place them in the tincture of iodine. Those 
portions which .were green are | 
now quite dark, while the V-shaped 
figure, or that part which was 
white, remains white in the iodine 
or does not take the dark colour. 
The green part of the leaf, then, 

forms starch. We have now learned 
that the leaf-green as well as sun- 

light is necessary to make starch. 
The leaf-green cannot make starch ~ 
in the dark, nor can the light make "Tr oieuriscomoved and 
starch in portions of a leaf which Ee oa ee 
have no leaf-green. 
Starch is formed in the green leaf during the day, but 
what becomes of it at night? In the afternoon let us 
cover a part of a leaf in such a way as to shut out the 
hight from that spot. Take two corks, place one on 
elther side of the leaf, covering a small circular portion, 
and thrust two pins through the edge of one cork to 
pin it fast to the other. From our former experiments 
we know that at this time of day all parts of the green 
leaf contain starch, so that the part covered by the 
corks, as well as the uncovered portion, now contains 
starch. On the following day at noon, or in the 
