Pneumatocyst

In phycology, a pneumatocyst is a floating structure that contains gas found on brown seaweed. A seaweed`s thallus may have more than one. They provide buoyancy to lift the blades toward the surface, allowing them to receive more sunlight for photosynthesis. The proportion of gases in the pneumatocysts varies depending on the physiological status....
Found on http://en.wikipedia.org/wiki/Pneumatocyst

Pneumatocyst

• (n.) A cyst or sac of a siphonophore, containing air, and serving as a float, as in Physalia.
Found on http://thinkexist.com/dictionary/meaning/pneumatocyst/

Pneumatocyst

Pneu·mat'o·cyst noun [ Pneumato- + cyst .] (Zoology) A cyst or sac of a siphonophore, containing air, and serving as a float, as in Physalia.
Found on http://www.encyclo.co.uk/webster/P/112
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