foliose (adjective; variant spelling: foliaceous) – general growth form of a "leaf-like" thallus, i. e., dorsiventrally oriented with a distinct upper and lower surface usually associated with internal thallus differentiation (heteromerous), rarely undifferentiated throughout (homoimerous). Foliose thalli are usually differentiated into lobes of various shapes, sizes and orientations. These thallus lobes are generally larger than somewhat arbitrarily distinguished as squamules. They vary in their attachment to the substrate from almost completely adnate to umbilicate; usually removable intact from the substrate, though sometimes with considerable difficulty. See also umbilicus, a crustose transition form. Related terms: lobe, lobule.