44 LEAVES 
the bottle. Put a hole, slightly larger than the petuole, 
thru a cork which fits the bottle; cut the cork in half 
thru the hole and close the bottle with it; put a little 
vaseline on the cork around the petiole, so as to make 
the bottle practically air tight. Set the plant in a well 
lighted place so that the leaves selected will be exposed 
to strong light. Late in the afternoon of a bright day, 
after the pieces of cork have been on the leaf two or 
three days, pick (1) the leaf to which the pieces of cork 
were fastened; (2) the leaf in the bottle; (3) a leaf 
which is partly white, a variegated geranium leaf; and 
(4) in the morning before daylight pick a third leaf from 
the plant to which the pieces of cork were fastened. 
Label these leaves I, 2, 3 and 4 by slipping their petioles 
thru small pieces of paper containing these numbers. 
Boil all the leaves two minutes as soon as they are picked 
and put them into a wide mouthed bottle containing 15 
c. c. 80 per cent. alcohol. As soon as the leaves are no 
longer green (one or two days) take them out, wash them 
and lay them on a white plate containing a weak solution 
of iodin, about 5 mm. deep. Kesult; conclusion? 
Exp. 30, Class: Invert a funnel over some aquatic 
plants in water (e. g. Elodea), lower the funnel until 
it is entirely under water, and fasten it. Fill a test tube 
and invert it under water, then raise it and slip it over 
the smaller end of the funnel. After several cubic centi- 
meters of gas have collected in the tube, test it with a 
glowing (not flaming) splinter. Results: conclusions? 
Exp. 31, Groups of Two: Break off two branches 
of Elodea 5 cm. long, fasten them to a glass rod 
and submerge them in a jar of water, about the tem- 
