V. THE LEAVES 



59. Structure of leaves. — Examine the leaves of 

 the oak, maple, beech, and willow on the stems. 

 The leaf will be found to consist of three principal 

 parts : the tase or portion by which it is attached to 

 the stem, the stalk or petiole, and the blade or lamina. 

 The base may take the form of a swelling of the 

 petiole, as in the locust, bean, or sumach, or it may 

 develop small, leaflike appendages, as in the willow. 

 Make an examination of the leaf of the willow and 

 draw to show results of observations. 



The petiole is generally in the form of a stalk or 

 stem, though it may be edged or winged, or it may 

 be absent, in which case the lamina of the leaf sits 

 directly on the stem. Find some plant the leaves of 

 which are lacking in petioles, and draw. 



The base and the petiole are for the purpose of 

 supporting the lamina in the proper position, and 

 conducting water and food to it. It is in the lamina 

 that the most important work of the leaf is done. 



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