In message . com,
Mareyn writes
Good afternoon,

My boss just came to me and asked, "Do you have any idea what the
"n.o." in front of a botanical family name means?"

Now, I probably knew the answer to this back when I was in college, but
it has since been purged from my mind. I've been looking through the
International Code of Botanical Nonmenclature trying to figure this
out, but I'm having no luck.

Does anyone happen to know the answer to this, right off the top of
their heads?

example: n.o. Aristolochiaceae

Thanks for your help!

It's new to me as well. In the absence of any context, I'd take a guess
that it might be "natural order".
--
Stewart Robert Hinsley