areolate (adjective) – subdivided into irregular, angular patches called areoles; referring either to the thallus surface or to the entire structure of a crustose thallus, i. e., the areolate growth form. (1) areolate growth form: a crustose thallus that is compartmentalized into distinctly separate areoles (patches, islands, areas). Primarily areolate thalli develop from aggregation of individual areoles, each single one distinctly delimited and typically lined with an intact cortex along its margin. Rimose-areolate thalli are secondarily formed when fissures of a rimose thallus merge and thus secondarily delimit areoles. These "pseudo-areoles" are usually not clearly delimited and they are never lined with an intact cortex. (2) areolate thallus surface: a surface of a foliose or fruticose thallus covered with irregular, angular patches. Not to be confused with the areolate crustose growth form. Areolate crustose thalli are entirely broken into areoles. Thalli with an areolate surface have a continuous thallus beneath the fractioned surface, e. g., foliose or fruticose thalli can have an areolate cortex, but they do not belong to the areolate growth form.