THE LEAF 



31. Parts of the Leaf. Examine a young, healthy leaf 

 of apple, quince, elm, etc., as it stands upon the stem, and 

 notice that it consists of three parts : 

 a broad expansion called the blade ; a 

 leaf stalk or petiole that attaches it to 

 the stem; and two little leaflike or 

 bristlelike bodies at the base, known 

 as stipules. Make a sketch of any leaf 

 provided with all these parts and label 

 them respectively blade, petiole, and 

 stipules. These three 



ii. -A typical leaf and P al " tS 

 its parts : b, blade ; /, peti- O r typical leaf, but as a 

 ole ; s, s, stipules. 



matter of fact, one or 

 more of them is usually wanting. 



32. Stipules. The office of stipules, 



when present, is generally to subserve 

 in some way the pur- 

 poses of protection. In 

 many cases, as the fig, 

 elm, beech, oak, magno- 

 lia, etc., they appear only as protective 

 scales that cover the bud during winter, 

 and fall away as soon as the leaf ex- 

 pands. When persistent, that is, en- 

 during, they sometimes take the form 

 of spines and thorns, as in the black 

 locust and spiny clotbur (Xanthium 

 spinosum}. The sheathing stipules of 



of -"prince's feather" (Po- the smartwceds and bindweeds (Polygo- 



lygonum oriental,) (G RA v). ^^ ^^ ^ strengthen ^ gtem ^ ^ 



joints (Fig. 13), and the adnate stipules (Fig. 14) of the 

 rose, clover, strawberry, etc., may serve either as water 

 holders or as shields against climbing insects. In the smi- 

 lax and some other vines they appear as tendrils for climb- 

 ing, while in other cases, as the garden pea and pansy, they 

 become large and leaflike, or may even usurp the place of 



