Effect of Environment on Germination of Ascospores of Urnula Craterium

SUMMARYAscospores of Urnula craterium were subjected to various environments to determine their effect on germination. Percentage germination and length of germ tube were used to determine the response. Ascospores germinated over a wide temperature range, including 5° and 35° C. The optimum, based on germ tube elongation and percentage germination 16 hours after expulsion from the apothecium, was 20–30° C. Germination of some spores occurred at 35°, but the protoplasm was extruded from both germ tubes and ungerminated spores. There was no subsequent growth. Added nutrients increased germination, but 85% of the ascospores germinated without them. There was no subsequent growth, however. Growth from germinated ascospores was excellent on malt extract agar and Barnett's agar; the optimum for continued growth was 24–27°. C. Ascospores germinated over a range of pH from 2.5 to 9.5; the optimum was 5.3 for germination and germ tube elongation. Light had no effect on germination, but it affected longevity. Germination of ascospores stored 383 days at 20–25° C was 10% for storage in light and 40% for storage in dark. The ascospores germinate in less than 2 hours and germ tube elongation is rapid at optimum temperatures.