Ascospore Discharge by Erysiphe Trina

SUMMARY

Ascospores appear to be the major if not the only means of dispersal of Erysiphe trina Harkn. on Quercus agrifolia Née. When living leaves bearing perithecia were wetted, spore discharge began in less than 10 min. Maximum discharge was in the first hour and continued for about 40 hr. Ascospores were discharged vertically to a maximum of 31 mm above the perithecia. Many ascospores disintegrated explosively in a moist chamber and the splash drops stained heavily with Sudan IV. At 21 C and 50% relative humidity the turgid ascospores decreased in volume more slowly than did conidia of Erysiphe polypgoni DC. or Erysiphe graminis DC.