The small constriction visible in the spathe occurs between female and male part of the inflorescence, which matures at different time. It is suppossed to trap the pollinators in the female part overnight until the pollen is ripened and drop onto the base of this constriction. When the constriction widens the pollinator gets a pollen shower before crawling out. Amorphophallus muelleri from Myanmar, Thailand and Sumatra. This plant is fairly robust in culture and can set seeds without pollination.
Seedlings are quite pretty, with pink leaf edges.
This photo comes from Dewey Fisk from Florida, click on the photo to goto his web-page. Some Amorphophallus show the ability to produce bulbous organs at aerial part of the plant - the picture shows the intercalary bulbils of Amorphophallus bufo just before the stem dries up. Amorphophallus asterostigmatus from Thailand. Parts of this plant are reputed to be used for curry making.