Gelidium

Gelidium is a genus of thalloid red algae comprising 134 species. Its members are known by a number of common names.

== Description and life cycle == Specimens can reach around in size. Branching is irregular, or occurs in rows on either side of the main stem. Gelidium produces tetraspores. Many of the algae in this genus are used to make agar. Agarocolloids are known to be extracted in algae belonging to the orders Gracilariales and Gelidiales with certain applications in the food and cosmetics. Gelling properties often differ among species, seasons, seaweed age, and substitutions between sulphate esters, among other compounds. Sulphate composition often dictates gel strength, while methyl esters determine gelling and elasticity.