Specialization of Parasitism in the Erysiphaceae. i2r 
of mycelium bearing more or less powdery groups of conidiophores 
on both leaves; controls still free. 
199a. September 21. Virulent infection of the three leaves, 
now covered with numerous patches of mycelium bearing a few 
young conidiophores. September 25. Vigorous groups of 
conidiophores on all three leaves ; controls free. September 30. 
The three leaves with numerous powdery masses of Oidium ; a few 
young (yellow) perithecia visible on two leaves; controls still free 
October 4. A few perithecia, some brown and nearly mature, on 
all three leaves, among the still densely powdery Oidium- patches. 
220a, 220e. September 30. Flecks of mycelium bearing a 
few young conidiophores oh two leaves. October 5. The six 
leaves densely covered with vigorous extended powdery patches of 
Oidium ; controls free. October 10. Large very powdery Oidium- 
patches on the six leaves ; on two of the leaves numerous young 
(yellow) perithecia among the conidiophores. 
229a. October 5. Small scattered patches of Oidium on the 
two leaves ; controls free. October 10. Large powdery Oidium- 
patches on both leaves. 
199b. September 25. A few conidiophores (about 7) visible 
on one leaf. September 30. One leaf apparently fully infected, 
and bearing very numerous but rather scattered conidiophores. 
October 4. On the one infected leaf one young (yellow) perithecium 
formed among the conidiophores ; controls all free. No infection 
of the other inoculated leaf. 
229b. October 10. On one leaf numerous scattered groups 
of conidiophores and patches of mycelium, in one place nearly 
powdery with masses of ripe conidia,—apparently full infection ; 
controls free. No infection of the other inoculated leaves. 
TABLE IX. 
Infection-experiments with conidia of E. Galeopsidis on 
Ballota nigra. 
Exper. 
No. 
Date 
1903 . 
Species used as Host. 
No. of 
leavesiuo- 
culated. 
No. of 
leaves 
infected 
208a 
Sep. 18 
Ballota nigra 
3 
3 
221a 
„ 23 
„ (seedlings) 
2 
2 
208b 
„ 18 
Salvia verticillata 
3 
0 
221b 
„ 23 
Leonurus Cardiaca 
2 
0 
Remarks. 
208a. September 25. Patches of mycelium with a few young 
conidiophores on all the three leaves ; controls free. September 28. 
The three leaves virulently infected, bearing continuous extended 
snow-white patches of densely crowded conidiophores; controls 
free. October 5. The three leaves covered with snow-white densely 
powdery O/rfw/H-patches ; a few flecks of mycelium now on one 
control. 
221a. October 5. Virulent infection apparent; both leaves 
covered with sno w-white densely powdery Oidium- patches; 
controls free. 
