PHYLLOTAXY 



VI. It is found very convenient to represent any of the 

 alternate or spiral arrangement of leaves such as the Begonia 

 by a common fraction. The number of turns of the spiral 

 is taken for the numerator, and the number of leaves passed 

 through for the denominator. What would be the fraction 

 for the Begonia? 



VII. Take a young plant of the White Hellebore ( Vera- 

 trum viride) and notice : 



1 . The three vertical ranks. 



2. That the spiral makes one revolution and passes through 



three leaves before it reaches the one directly above 

 the one from which it started. 



3. What fraction will express the phyllotaxy of this three- 



ranked arrangement? 



4. Make sketches of the White Hellebore, including views 



from the side and from above. 



VIII. Examine the arrangement of the leaves upon a ver- 

 tical branch of the Apple or Pear Tree, noticing : 



1. The number of leaves at each node. 



2. The number of leaf-insertions passed through to reach 



one exactly above the one from which you start. 



3. The number of revolutions of the spiral. 



4. Make a diagram to show this. 



5. What is the fraction representing this arrangement? 



6. What should the number of vertical ranks be? 



7. Do you notice any twisting of the internodes so as to 



make the determination of the phyllotaxy difficult? 



IX. Examine a vertical branch of Holly or of Pittosporum 

 i . Find the number of vertical ranks. 



