Previously bleached leaves are re-exposed to sunlight. Observations are made on whether the chloroplasts become more numerous, or does each one become more green. Sterile agar plates will be opened prior to and after the students arrive in the classroom for the first time in the day. Elodia is bunched and the middle third of their leaves are wrapped to block light, and they become chlorodic. Later, the leaves are laid horizontally in bright light.
Bubbles rise only from the green areas.
The gas is collected in inverted tubes and later determined by chemistry to be oxygen. Discussions then can be done on what flies might be carrying on their feet. A number of different small organisms to inspected. Others are even smaller - yeast. And yet others are very small - prokaryotic bacteria.