Term derived from the Classical concept of forms created by the power of natural life, applied to the use of organic shapes in 20th-century art, particularly within Surrealism. It was first used in this sense by Alfred H. Barr jr in 1936. The tendency to favour ambiguous and organic shapes in apparent movement, with hints of the shapeless and vaguely spherical forms of germs, amoebas and embryos, can be traced to the plant morphology of Art Nouveau at the end of the 19th century; the works of Henry Van de Velde, Victor Horta and Hector Guimard are particularly important in this respect.