CHAPTER III. THE LEAF. 



25 



leaf grow down the sides of the stem, or become decurrent, as 



in the Mullein, the Sneeze-weed and the Comfrey, Fig. 49. 



But even the blade, 

 although the most im- 

 portant part, may be 

 wanting or developed 

 into some form differ- 

 ent from the ordinary 

 one, while either the 

 stipules or the modi- 

 fied petiole performs 

 its functions. Lathy- 



j^Jr *LJj rus aphaca, Fig. 50, is 



an example of a leaf 

 in which the stipules 

 become strongly de- 

 veloped and perform 



the functions of blades, while the petiole and blade proper are 



Fig. 49- Fig. 50. 



Fig. 49. — Decurrent leaf of Comfrey. 



Fig. 50. — Portion of stem of Lathyrus aphaca, one of the 

 Pulse family, showing stipules which perform the functions 

 of a leaf-blade while the blade proper is developed into a 

 tendril. 



Fig. 51. 



Fig. 52. 



Fig. 51. — Leaf of Australian Acacia, showing tendency to abortion of leaf-blade and 

 the development of the petiole into a phyllode. 



Fig. 52. — Fully developed phyllode of Australian Acacia. 



