EXERCISE 135 



Problem. How does the natural fall of leaves differ from the breaking off of leaves ? 



What to use. Twigs of deciduous trees bearing leaves and showing old leaf scars ; magnifying glasses ; 

 microscope ; prepared slide. 



What to do. Study several of the old leaf scars. Break off one or two leaves near the base of the 

 petiole (leafstalk) and study the scars left. Study sections through base of petiole with microscope. 



Record. Make a large drawing of a typical natural scar and of one resulting from tearing off the leaf. 

 Make a drawing of section through the scission (splitting) layer as seen with the microscope. 



Questions. 1 . What region of the petiole is most easily broken ? 



2. What marks the region that separates when the leaf falls ? 



3. How does the surface of the natural scar differ from that of the artificial scar ? 



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