CHAPTER IV 



THE STUDY OF THE SHOOT (Continued) 



Parts present in a Perfect Foliage Leaf. In a perfect 

 leaf the following parts are present. 



The blade or the fully expanded portion of the leaf. 

 I\\R petiole or the stalk of the leaf. 



The Sheath which forms the base of the leaf. It is wider than 

 the petiole, and may sheathe the stem. 



In most cases the blade is present ; when other parts of the 

 leaf are absent, the leaf is said to be sessile, as in the Wall- 

 flower. If the sheath is not developed, but 

 the blade and petiole are present, the leaf 

 is called petiolate, as in the Cherry. If all 

 the parts are present, as in the Pilewort and 

 Arum, the leaf is perfect. Outgrowths may 

 be produced from the base of the leaf, as in 

 the Rose and the Pea ; these are termed 

 Stipules. If stipules are present the leaf is 

 said to be stipulate, and if they are absent 

 exstipulate. 



The Venation of Leaves. The veins 

 of a leaf form the framework by which the 

 softer parts are supported ; they also bring 

 the sap from the stem and distribute it to 

 the cells of the leaf. Leaves may either be 

 parallel or reticulate veined. The former 

 arrangement is found in monocotyledonous plants and the 

 latter in dicotyledonous. In a parallel- veined leaf, the veins 

 run parallel to one another from the base of the blade to 



-B 



FIG. 34. Perfect leaf 

 of Arum. B = 

 blade ; P = peti- 

 ole ; sh =sheath. 



