macrolichen (noun, pl. macrolichens; opposite: microlichen) – a lichen with a large thallus. Though sometimes adopted for convenience, it is not reasonable to distinguish lichens by size. Most commonly fruticose and foliose lichens are referred to as macrolichens, but this distinction is completely arbitrary. Growth form is not at all correlated with size. Some fruticose lichens are very minute and crustose thalli can extend across immense areas. It is often argued that the distinction is reasonable assuming that large thalli, and thus fruticose and foliose species, would be more easily identified. However, many macrolichens like species of Usnea or Cladonia display an enormous morphological variability and their reliable identification often requires the analysis of the secondary chemistry.