HYPOCREALES 193 



According to Falck (1911), the ascospores are violently dis- 

 charged into the air and then are carried by convection currents 

 to grass flowers. This method of spore dispersal has been verified 

 by several observers by means of the beam-of-light method. 

 Stager (1903), however, maintains that the spores are slowly 

 exuded from the perithecia to form a sHmy layer. Then dispersal 

 is facilitated by insect visitors, especially flies and beetles. Some 

 idea of the profligacy of ascospore production can be gained 

 from Kiinn's calculation [Atanasoff (1920), p. 29] that a scle- 

 rotium with fifteen stromata will produce over a million asco- 

 spores. 



The exact manner in which the ovary becomes infected is not 

 known. There is reason to beheve that germ tubes from asco- 

 spores lodged on the glumes cannot penetrate them. If the 

 glumes are open so that the ascospores lodge on the stigmata or 

 in the nectar, they should germinate, and the germ tube should 

 extend into the ovary. Experiments by Stager (1903) indicate 

 that infection takes place both in polHnated and non-pollinated 

 flowers. When he inoculated the ovaries 3 or 4 days before 

 flowering, he found that infection developed very rapidly. In- 

 fection is indicated by the investment of the ovary with a super- 

 ficial weft of mycelium. The ovarian tissues are penetrated, how- 

 ever, and become completely replaced by a furrowed, porous 

 mass that will eventually be the sclerotium. Meanwhile the sur- 

 face of the mass is densely covered with elongated cells from 

 whose apices conidia are abstricted. This constitutes the spha- 

 celial stage. The conidia are formed in great numbers and col- 

 lect in droplets that appear at the edges of the glumes. These 

 droplets are the "honey dew" which is sweet to the taste, and, if 

 examined microscopically, will be found to be teeming with mil- 

 lions of ellipsoidal hyaline conidia. Honey dew is attractive to 

 flies and other insects that incidentally aid in disseminating the 

 conidia to cause secondary infections. Dew and rain also serve 

 to convey conidia to other grass flowers. 



Different explanations have been given to account for the 

 origin of honey dew. Some workers believe that it is secreted 

 by the sphacelial hyphae, and others that it is secreted by the 

 nectaries in response to stimulation by the ergot fungus. 



The time required for the formation of sclerotia is correlated 

 with the weather. In moist weather sclerotia may first be appar- 



