184 



SPORE DISSEMINATION 



conidia of the entomogenous fungus, Entomophthora imiscae. 

 When the fly, sluggish because of the infection, succumbs, rhi- 

 zoidal hvphae grow out from crevices between the sclerites and 

 anchor the fly to the pane. Expulsion of conidia by this fungus 

 and most other species of Entomophthora is accomplished by the 

 same mechanism. In a report Sawyer (1931) described this type 

 of spore discharge in Entomophthora sphaerospenna, parasitic on 



Fig. 30. Stages in spore discharge by Entomophthora sphaerosperma. A. 

 Conidiophore with papillar apex. B. Bud-like enlargement at the apex of 

 conidiophore. C. The conidium has been delimited bv a septum, and 

 there occur two closely opposed membranes. D. The conidiophore tip im- 

 pinges into the conidium that has just been freed. E. The tip of the 

 conidium becomes everted after release of pressure from conidiophore. 



(After Sawyer.) 



the larvae of Rhopobota vacciniana, attacking cranberries, Vac- 

 cinium vmcrocarpon. He noted that a bud, the initial of the 

 conidium, forms at the blunt apical portion of the conidiophore. 

 Into this developing conidium a nucleus passes, the conidia! wall 

 thickens, and a short neck becomes differentiated between coni- 

 dium and conidiophore. A septum then forms across the base 

 of the spore. This septum consists of two membranes in close 

 apposition, one being the basal wall of the conidium, the other 

 the apical wall of the conidiophore. As growth continues, the 

 greater hydrostatic pressure within the conidiophore forces the 

 opposed walls to bulge convexly into the conidium. Eventually 

 the pressure becomes so great that the attachment between the 

 conidium and the conidiophore is ruptured circumferentially. 



