PHYLLOTAXY 



1. The three ranks of sessile leaves. 



2. The very short internodes. 



3. The spiral course of each rank. 



4. This seems, at least, an entirely different thing from the 



secondary spirals of the cones we have examined. 



XVII. Examine branches of some species of Pine and of 

 the Larch or Deodar and notice : 



1. The leaves, arranged in small bunches ex fascicles. (Two 



to five in the Pines, a larger number in the Larch 

 and Deodar.) 



2. These leaves really belong to short branches whose inter- 



nodes are so short as not to be visible. 



3. Make sketches of ^^fasciculate leaves. 



XVIII. Questions upon Phyllotaxy. 



1. What is phyllotaxy? 



2. In what two different sets of ways may leaves be ar- 



ranged upon the stem? 



3. What name do we give to each? Why? 



4. Describe some varieties of the cyclical arrangement. 



5. What is meant by the spiral arrangement? 



6. How may any spiral arrangement be expressed in the 



form of a fraction ? 



7. Give the series beginning ^-, \, etc. 



. 8. How does torsion of the internodes affect the phyllotaxy ? 

 9. Describe the differences between the arrangement upon 



vertical and upon horizontal branches. 

 10. What is meant by fasciculate leaves? Give and explain 



examples. 



n. Why should there be such a variety in the phyllotaxy 

 of the different plants? 



