Since I posed the original question, I can say w/ authority that the
fruits were restricted to fleshy animal-dispersed fruits. I have no idea
whether the premise of the question is even true. But perhaps it's true
that these sorts of fruits tend not to be thread-like, or flat, or
rings. I guessed that one of the explanations would have to do with how
fruits develop or enlarge. If the simplest program is to enlarge a small
group of cells, maybe that would tend to make fruits end up round? But
probably plants' developmental programs aren't THAT constrained...
Anyway, I've really been enjoying all the ideas people have had, and have
passed them along to the math guy who asked in the first place.
Anne Heise
Washtenaw Community College
Ann Arbor MI
