pneumatophore

Noun

 * 1)  A gas-filled sac or float of some colonial marine coelenterates, such as the Portuguese man-of-war.
 * 2)  An aerial root, in mangroves etc., specialized for gaseous exchange.
 * 3) An apparatus consisting of a bag with a tube and mouthpiece, which may be attached to the body. The bag contains oxygen to be breathed by the wearer in rescue work in mines, etc.

Adjective

 * 1) pneumatophorous