a prefix meaning "opposite", "inverse" or "against". When used as a prefix before a word describing the shape of an organ, it means that the organ is attached to its stalk at the opposite end to the usual case.
Copyright: Mark Hyde, Bart Wursten, Petra Ballings and Meg Coates Palgrave, 2002-17
Hyde, M.A., Wursten, B.T., Ballings, P. & Coates Palgrave, M.
. Flora of Zimbabwe: Glossary details: ob-.
http://www.zimbabweflora.co.zw/speciesdata/glossary-display.php?glossary_id=469, retrieved 30 March 2017