The effects of different concentrations of nitrate and phosphate on the microscopic stages of development of Lessonia nigrescens Bory were studied. Meiospores were cultivated under different concentrations of nutrients (0 to 100 μmol N·l −1, and 0 to 1.00 μmol P·l −1) and optimal light and temperature conditions. The successive stages of development have different nutrient demands. Meiospore germination occurred in all the nitrate and phosphate concentrations tested, the germination percentage was not significantly modified by the different nutrient amounts. Although gametophytes developed in all conditions, their patterns of development and fertility varied. When no nutrients were added, gametophytes remained unicellular and sterile. Depending on the interacting effects of the amounts of nitrate and phosphate added to the culture media, few-celled or multicellular gametophytes developed. The highest gametogenesis was found in the conditions favouring few-celled gametophytes. In the conditions inducing filamentous gametophytes, gametogenesis was delayed or inhibited. Sporophytes developed only in very precise and restricted conditions. The results, however, suggested that fertilization was the process requiring the most precise conditions; once sporophytes developed, even when only in small numbers, most of them showed normal patterns of growth.