XVI International Botanical Congess

The existence of viable fern spores in four different soil levels from tropical forest and clearings of the same forest at the Tropical Biology Station in Los tuxtlas was proven. Humid soil from each one of the levels was put in plastic trays, under 12 h light/12h darkness, 21-25 ?C. After 18 months of culture, the higher density of gametophytes was found in soil from 0-5 cm depth and it was very low in soil from 25-35 cm depth. After two years, sporophytes of Pityrogramma calomelanos, Lygodium heterodoxum, Nephrolepis cordifolia, Hemionitis palmata and Thelypteris sp. have been identified at the four levels studied. The sporophytes of N. cordifolia in cultures in soil from tropical forest reached 25 cm tall, while those of soil from clearings reached 15 cm tall. It is concluded that the viability of the spores is affected for biological, climatic and edaphic variables: age of the spore, solar radiation, temperature, humidity, texture, porosity, aireation and soil drainage as the most important.