The Corpse Flower grew another 2.5 inches yesterday, and is now 39.5 inches (100 cm) tall. It will probably just about double in height over the next couple of weeks. Since the flowers are borne without foliage (i.e., the leaves are "hysteranthous"), most of that floral mass is coming from stored carbohydrates in the underground corm. Given the history of this plant, those carbohydrates were synthesized way back in summer 2006, the last time the plant had a leaf.
Actually, there isn't quite as much biomass in an A. titanum inflorescence as you might guess. The whole structure is quite spongy, with a lot of air spaces, and the spadix (the central pointy bit) is nearly hollow. Also, this species does grow roots when flowering, so some of the water content of the inflorescence is undoubtedly fresh from the soil. Other Amorphophallus species, like A. konjac, flower when rootless, so even the water in the bloom must be taken from stored reserves.