We recently visited Tarpon Springs, Florida where we learned a lot about sponges. We learned that Loofa, also spelled Luffa, is actually a vegetable.
You can see a picture of a luffa on the vine at http://en.wikipedia.org/wiki/Luffa. The write-up says:
The luffa, loofah, or lufah (from Arabic لوف) are tropical and subtropical vines comprising the genus Luffa, the only genus of the subtribe Luffinae of the plant family Cucurbitaceae. The fruit of at least two species, Luffa acutangula and Luffa aegyptiaca (Luffa cylindrica), is grown, harvested before maturity, and eaten as a vegetable, popular in Asia and Africa.
The ripe, dried fruit is also the source of the loofah or plant sponge. Luffas are also used to make the soles of beach sandals.
Visit the SpongeOrama Web site for more information at http://www.spongeorama.com/