THE WALLFLOWER 



15 



The whole length of the stem is divided into 

 nodes and internodes. The part where a leaf is 

 borne is called a node, the spaces between the leaves 

 are the internodes. 



Each leaf is attached to the stem by a narrow 

 base. It has no distinct stalk, but the blade of the 



FIG. 6. Diagram to illustrate f Phyllotaxis. The dotted 

 line represents the leaf-spiral, which is seen in horizontal 

 plan, the centre corresponding to the apex. The con- 

 centric circles represent the successive nodes. (After Van 

 Tieghem.) 



leaf is very narrow near the base, and broadens out 

 quite gradually for about two-thirds of the whole 

 length, and then narrows again rather more rapidly 

 to the pointed end. The leaf is technically called 

 sessile, because the blade is seated on the stem directly, 

 without the intervention of a leaf-stalk or petiole, such 



