CHAP. VI LEAVES 35 



of a flattened petiole without a blade. If a specimen of 

 Lathyrus Aphaca (either fresh or pressed) can be obtained, 

 examine its leaves and notice : 



1. The absence of blades ; 



2. The prolongation of the petioles into tendrils; and 



3. The increase in size of the stipules (to make up for the 



loss of the blade). 



4. Make a sketch of one leaf. 



VI. Many plants have leaves without distinction of parts ; 

 e.g. examine and sketch : 



1. The needle-shaped leaves of a Norway Spruce or a 



Pine. 



2. The awl-shaped and scale-shaped leaves of the Arbor- 



Vitse or the Lawson's Cypress. 



VII. Examine a rootstock of Iris to which the leaves are 

 attached. Notice that : 



1. Each leaf stands erect and presents its tip to the sky. 



How does this compare with the ordinary leaves ? 



2. Each leaf is folded together lengthwise so that the upper 



surface (or what corresponds to it) is inside, fr 



3. Make a sketch. 



VIII. Examine one of the upper leaves of a Eucalyptus. 

 Notice that : 



1. The two surfaces are vertical (instead of horizontal). 



2. This is brought about by a twisting of the petiole. 



3. Examine the leaf of a young Eucalyptus and notice that 



it has a horizontal position instead of a vertical one. 



4. What are the reasons for these two positions? 



5 . Sketch each leaf to show its position. 



