The role of different temperatures on the germination of spores of 5 spp. of Cyatheaceae was analyzed. Lophosoria quadripinnata and Trichipteris bicrenata had the widest tolerance to extreme temperatures, while T. scabriuscula had a reduced range of tolerance. A rough correlation can be established between the temperatures where the species grow best and its general distribution in America. [The 2 other species studied were Nephelea mexicana and Cyathea fulva].