Aristolochia onoei Franch. & Sav.

Distribution : Japan
Picture 3 in Japan, Honshu, road to Mt. Rokko, May 2008
(Picture 8 with flowers of Clematis japonica)
(Picture 9 with flowers of Hydrangea hirta)

Description in Acta Phytotax. Geobot. 1939, viii. 50