2nd ranker in most beautiful and rarest flower list is

Amorphophallus titanum (Corpse flower ) Family - Arecaceae

It is the largest and smelliest flower in the world. It produces a rotten meat like odor. Corpse flowers can be only found in few Islands of Indonesia, in low lying rain forest areas.Corpse flowers are only blooms in every 30 or 40 years. The leaf of corpse flower grow up to the height of 20 feet. The flower of corpse flower appears to be green outside and dark red in inside. As it became very rare the botanical gardens where corpse flower grows mainly Sumatra gardens protected under law.