The distribution of Chondropsis semiviridis (FvM. ex Nyl.) Nyl. was mapped for Australia. Studies in gas exchange physiology demonstrated that length of drought is likely to limit distribution of the species. Similarly, it is shown that sensitivity to heat when wet is likely to prevent the species from establishing in arid areas with a summer rainfall seasons The surge of respiration upon wetting of lichen thalli noted by other workers was so short for C. semiviridis that it could not affect the limits of its distribution.