Amorphophallus muelleri

The following info has been extracted from Aroideana, Volume 19, a publication of the International Aroid Society.  You'll note that this is just a small portion of the extensive descriptive information available in the Aroideana 19:

Tuber up to 28 cm in diameter
Leaf petiole 40-180 cm long, 1-8 cm in diameter (base)
Leaf lamina 75-200 cm in diameter
Spathe 7.5-27 cm long, 6-27 cm in diameter
Spadix 8-30 cm long
Dormancy Not listed in volume 19, but mine survived out of the pot during one dormancy

(extracted with permission from Aroideana volume 19)