Agar, Fine Ground U.S.P.,
Gelidium 700AM, gelling agaent for making agar plates. Does not contain nutrients.
Agar is a galactose polymer (or agarose) obtained from the cell walls of some species of red algae or seaweed (Sphaerococcus euchema) and species of Gelidium. It is also known as Kanten, Agar-Agar, or Agal-Agal (Ceylon Agar).

Added at a rate of 1% to 2% can convert any water based liquid to gel.

More about Agar:
Chemically, agar is a polymer made up of subunits of the sugar galactose == ; it is a component of the algae's cell walls. Dissolved in hot water and cooled, agar becomes gelatinous; its chief use is as a culture medium for microbiological work. Other uses are as a laxative, a vegetarian gelatin substitute — a thickener for soups, in jellies, ice cream and Japanese desserts such as anmitsu, as a clarifying agent in brewing, and for sizing fabrics.