clarification of phyllotaxis

Grant R. Cramer cramer at MED.UNR.EDU
Thu Nov 20 18:55:12 EST 1997

Hi all,

 I am hoping one of you can enlighten an ignorant soul. I have been
teaching my class about phyllotaxis using  the text "Botany' by Moore et
al. They define phyllotaxis as the number of turns of a spiral/number of
leaves BETWEEN successive leaves of an orthostichy. As I went to expand on
this subject by giving an example from Esau's "Anatomy of Seed Plants", I
discovered that she describes 5/13 phyllotaxy as "five windings about the
axis include 13 leaves with leaves n and n plus 13 located one above the
other". That is there are only 12 leaves BETWEEN successive leaves of the
orthostichy. These two definitions are slightly different but important.
The other surprise was that the phyllotaxis was 5/13 not 8/13, which is
what I expected based on the Fibonacci series and how it is explained in
Moore et al.

My question is "What is the correct definition of phyllotaxis" or is there
no agreement on this?

Grant R. Cramer
Associate Professor
Department of Biochemistry, Mail Stop 200
University of Nevada,
Reno, NV 89557
Phone (702) 784-4204
Fax (702) 784-1650
email: cramer at

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