LABORATORY PRACTICE 



XV. Defoliation or the Fall of the Leaf. Examine va- 

 rious leaves as they are falling or after they have fallen and 

 notice how they separate from the branch which bore them. 



1. The Willows, Elms, Maples, Alders, and Hazels. The 



leaves separate from the stem at the base of the 

 petiole and fall off, leaving a clean scar. This is 

 characteristic for simple leaves. 



2. The Rose or the Locust-Tree, having pinnately com- 



pound leaves. The leaflets usually fall away first, 

 leaving the petiole and axis, and this falls later, 

 separating from the stem at the base of the petiole. 



3. The Horse-Chestnut or the Buckeye, having palmately 



compound leaves, may behave in either of two ways. 

 (ci) The whole leaf may separate at the base of the 



petiole and fall ; and then the leaflets fall away 



from the apex of the petiole ; or 

 (b) The leaflets may fall away from the petiole while 



it is still attached to the tree, the petiole itself 



falling afterward. 



4. It may be seen that the blade does not separate from 



the petiole in simple leaves, but does in compound 

 leaves. 



5. Notice that the blade of the leaf of the Grape Vine, or 



of the Japanese Creeper, falls away from the petiole. 

 This shows that the apparently simple leaf of the 

 Grape Vine, or of the Japanese Creeper, partakes of 

 the nature of a compound leaf. (Some nearly re- 

 lated vines and creepers have compound leaves, and 

 some of the leaves of the Japanese Creeper may be 

 compound.) 



6. Make sketches and notes. 



