the subject was CO2.... ie Carbonic Acid trees take in..the crap we put into the air and water we should Thank them for it.. burning trees that sponge up our toxics is not very Wise <A HREF="http://www.engg.ksu.edu/HSRC/97abstracts/doc44.html" target="_blank">http://www.engg.ksu.edu/HSRC/97abstracts/doc44.html</A>