You don't mean something like this do? It would not be invisible to the naked eye so I am thinking this is not what you have but thought I would doublecheck anyway.

Here is a link that might be useful: {{gwi:1301245}}

Thanks farkee, I believe that may be what I saw. When I looked at the leaf without the loup I could't see it and there was only one on each leaf that I examined. I'll look closer tomorrow.
Thanks for the education.