APPENDIX Vni 723 



Appendages dark brown for more than half their length, ultimate branches 

 of the apex knob-shaped, i oxyacantha. 



Key to Species of Erysiphe (After Salmon) 



Brief Characterization. — Perithecia globose, or globose-depressed, sometimes be- 

 coming concave; asci several, two- to eight-spored. Appendages floccose, simple 

 or irregularly branched (never with a definite apical branching) sometimes obsolete, 

 usually more or less similar to the mycelium and interwoven with it, very rarely 

 (£. tortilis) brown, assurgent and fasciculate. 



1. Asci (of mature perithecia) not containing spores on living host plant. (2) 

 Asci (of mature perithecia) containing spores. 



2. Perithecia large, 135 to 28o;j in diameter, averaging 200/i, more or less im- 

 mersed in the lanuginose persistent mycelium. 4 graminis. 



Perithecia smaller, 80 to 140M, not immersed in the lanuginose mycelium. (3) 



3. Haustoria lobed. 3 galeopsidis. 

 Haustoria not lobed. 2 cichoracearum. 



4. Asci two-spored, rarely (and never uniformly) three-spored. (5) 



Asci three- to eight-spored, rarely (and never uniformly) two-spored. (8) 



5. Perithecia 52 to 6o;i in diameter; asci three, 48 to 50 by 28 to 36/1. 8 trina. 

 Perithecia 80 to 240/1 in diameter; asci more than three, larger. (6) 



6. Perithecia large, becoming pezizoid, 13s to 240/1 in diameter, usually about 

 200/1; asci seven to thirty-eight, usually about twenty, 75 to iio/i long, 

 averaging 90/1, spores 28 to 40/1 long, averaging 32 by 18/1 long. 6 taurica. 

 Perithecia 80 to 140/1 (very rarely 100 to 175); asci four to twenty-five (very 

 rarely as many as thirty-six), usually ten to fifteen, 58 to 90/1 long; spores 

 20 to 28/1 long, averaging 34 by 14/1. (7) 



7. Haustoria lobed. 3 galeopsidis. 

 Haustoria not lobed. 2 cichoracearum. 



8. Perithecia 65 to i8o/j in diameter, usually about 90/1; asci usually few, two 

 to eight, rarely as many as twenty-two, 46 to 72 (rarely 8o)/i long, (g) 

 Perithecia larger, 130 to 280/1 in diameter, averaging 180 to 200/1; asci, nine 

 to forty-two, 70 to 115/1 long. 



9. Appendages very long, ten to twenty limes the diameter of the perithecium, 

 assurgent and fasciculate. 5 tortilis. 



Appendages long or short, spreading horizontally, often interwoven with the 

 mycelium, i polygoni. 



10. Perithecia more or less immersed in the lanuginose persistent mycelium. 

 4 graminis. 



Perithecia not immersed in a lanuginose persistent myceUum. (11) 



11. Spores four to six, 20 to 22 by 10 to 12/1. i polygoni var. sepulta. 



Spores eight, rarely six or seven, somewhat roundish, 16 to 20 by 10 to 15/1. 

 7 aggregata. 



