THALLUS GROWTH ASYMMETRY AND HABITAT INCLINATION IN LASALLIA-PUSTULATA

The relationship between thallus shape and habitat inclination in the umbilicate lichen Lasallia pustulata is investigated. There is a signi ficant relationship between the steepness of the habitat rock surface and the degree of asymmetry around the central holdfast of the thalli. This is interpreted as an effect of gravity, including the gravity-in fluenced over-under 'tiling' of the lichens on the habitat surface. Th ere was no correlation between thallus size and degree of asymmetry.