THE FALL OF THE LEAF 



273 



the vessels ' and fibres snap across. Let us suppose 

 that we hold in our hand a slender fishing-rod, and 

 switch it to and fro. It sways in gentle and continuous 

 curves, and unless it is loaded, it will not easily break. 

 Now suppose that we case the rod in a layer of plaster 



vb 



FIG. 66. Section through leaf-base of Horse Chestnut, before fall of the leaf. 

 X 25. /, wood ; Is to Is, leaf-stalk ; vb, vascular bundles ; s, corky layer. 



of Paris an inch thick, which is ringed, or cut com- 

 pletely through, in one place. What effect will the 

 plaster casing have upon the strength of the rod, and 

 upon its power to resist fracture by bending? Our 

 first thought will probably be that the plaster may 



T 



