Algae are plants of the order Thallophyta (Endlicher-1836). Algae vary greatly in terms of color, structure, flagella, habitat and stored food. Algae that grow underwater in soil are called benthic algae. Algae that grow on rocks are called lithophytes. Algae that grow on plants are called epiphytes and algae that grow inside plant tissues are called endophytes. Algae are called halophytes if they grow in brackish water in seas or oceans, cryophytes if they grow on ice or snow, thermals if they grow in hot springs and fungi if they grow with fungi. Algae that grow outside the animal body are called epizoic and algae that grow inside are endozoic.