PLATE 4. 



Erysipheae. 



Podosphaera tridactyla, (Wallr.). 



Fig. 1. Natural size on leaf of Morello cherry. 



2. An enlarged perithecium. 



3. Two asci. 



4. Four sporidia. 



5. A chain of conidia. 



0. Two conidia germinating. 



