EXPLANATION OF PLATES. 

 Plate I. The round of life in the Erysiphaceae. 



Germination of an ascospore. 



Portion of mycelium with conidiophore and chain of conidio- 



spores. 

 Germination of a conidiospore. 

 Tips of two hyphae with cross walls. 



Later stages of same with oogone and antherid well begun. 

 6. Oogone and antherid fully developed. 

 Conjugation. 



Carpogone with first layer of cover cells. 

 g. Carpogone with two layers of cover cells. 

 Fig. io. Elongation and division of carpogone. 



Fig. II. Perithecium with outer and inner walls, rudimentary append- 

 ages, ascus and ascospores. 

 Fig. 12. A single ascus with ascospores. 



Figures 6-io are modified after Harper and others. 



Plate II. General structure. 



Fig. 13. Perithecium of Microsphacra with appendages. 



Fig. 14.' Perithecium of Uncinula with appendages. 



Fig. 15. Tip of an appendage from Microspliacra grossiilariac. 



Figs. 16 and 17. Haustoria. 



Fig. 18. Perithecium of PodospJiaera with appendages. 



Figs. 19, 20 and 21. Variations in the tip of the appendage of Uncinula. 



Fig. 22. Perithecium of Erysiphc or Sphaerotheca with appendages. 



Fig. 23. Perithecium of Phyllactinia with appendages. 



