Orange

Excellent

Classic find. Also definitely worth a visit: "Carbon dioxide (CO2) is the principal gas that trees and other plants need to survive, just like oxygen (O2) is the principal gas that humans and other animals require. Trees absorb CO2 and release O2 -- animals inhale O2 and exhale CO2. See how nice this all works! Earth's first, primitive forests made their prolific debut 300 million years ago during the Carboniferous Period. Before then, the atmosphere held far more CO2 but concentrations declined throughout the Carboniferous Period as plants flourished. During the Carboniferous Period the atmosphere became greatly depleted of CO2 (declining from about 2500 ppm to 350 ppm) so that by the end of the Carboniferous the CO2-impoverished atmosphere was less favorable to plant life and plant growth slowed dramatically."