I'll pass along a recommendation I got from David Becker at Pomona
College. It's actually an "illustrated glossary".
"Plant Identification Terminology: an Illustrated Glossary" by James
G. Harris and Melinda Woolf Harris. 1994. Spring Lake Publishing,
Payson UT. QK9.H37
In addition to the beautifully illustrated glossary, it has sections
on specific terminology for leaves, inflorescences, flowers etc. I
just checked and it's available from Amazon in paperback for $16.
Associate Professor of Biology
Harvey Mudd College
"not affiliated with authors or publisher!"