Agar is a jelly-like substance consisting of polysaccharides obtained from the cell walls of some species of red algae, primarily from "ogonori" (Gracilaria) and Gelidium. It is commonly used in Asian cuisines as a vegan substitute for gelatin, as a thickener for soups, in fruit preserves, ice cream, and other desserts, and as a clarifying agent in brewing. In microbiology, agar is used as a solid substrate to contain culture media for microbiological work. Agar plates can be selective and can be used to promote the growth of bacteria of interest while inhibiting others. Agar was first described for use in microbiology in 1882 by the German microbiologist Walther Hesse, an assistant working in Robert Kochs laboratory, on the suggestion of his wife Fanny Hesse. Agar quickly supplanted gelatin as the base of microbiological media, due to its higher melting temperature, allowing microbes to be grown at higher temperatures without the media liquefying. Agar is also used as a solidifying agent in plant growth media for plant tissue culture.