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respiration and accelerates the decomposition of chlorophyll in 
some fruits and leaves. Ethylene injury to plants can be distin- 
guished from the injury caused by such toxic gases as sulphur 
dioxide, hydrogen sulphide, and ammonia. The latter gases cause 
the rapid killing of tissue, while ethylene causes injury largely by 
stimulating growth, or metabolism, and never shows quick killing 
or burning of the tissue. It stimulates growth of the abscission 
layers which produce the fall of petals or leaves or the extra 
growth on the upper side of the petioles of many plants which 
leads to epinastic response. It causes the development of in- 
tumescent growth on some stems and roots. In the rose, gardenia, 
Doctors Zimmerman, Hitchcock and Crocker have made a 
study of more than 100 species and varieties of plants commonly 
in pure air. It will also stimulate the fall of the cherry in a oa 
culiar way, that is, by developing an abscission layer in the pedun 
g of 
