Specialization of Parasitism in the Erysiphaceae. 119 
TABLE VI. 
Infection-experiments with conidia of Sphaerotheca Humuli 
var. fuliginea on Taraxacum officinale. 
Exper. 
No. 
Date 
1908 . 
Species used as Host. 
No. of 
leavesino- 
culated. 
No. of 
leaves 
infected. 
172a 
Sept. 8 
Taraxacum officinale 
(young potted plants). 
3 
3 
172c 
„ 8 
Taraxacum officinale 
(young potted plants). 
3 
3 
176a 
„ 10 
Taraxacum officinale 
(young potted plants). 
3 
3 
172b 
„ 8 
Plantago media 
(young potted plants). 
3 
0 
17 2d 
„ 8 
Plantago media (seedlings) 
• 3 
0 
176b 
„ 10 
,, (young potted plants) 
3 
0 
172e 
„ 8 
P . lanceolata (young potted plants) 
3 
0 
176c 
„ 10 
M >1 
3 
0 
176d 
„ 10 
Fragaria sp. (cult.) „ 
3 
0 
Remarks. 
172a and 172c. September 21. Numerous scattered comdio- 
phores at the inoculated places on the six leaves ; controls free. 
September 25. All six leaves virulently infected; numerous 
vigorous Oidium- patches, powdery with masses of ripe conidia ; 
controls still free. September 29. On all six leaves the fungus 
everywhere passing from the conidial stage into the ascigerous 
stage; already many hundreds of nearly mature brown perithecia 
on each infected leaf, as well as young just-formed pale-green 
ones; controls still free. October 4. All the six leaves with 
extended patches of crowded dark-brown ripe perithecia, each 
containing a mature ascus with spores. 
176a. September 23. Little scattered groups of conidio- 
phores on all three leaves; controls free. September 25. More or 
less powdery Oidium-patches on all the three inoculated leaves ; 
controls still free. September 29. Oidium -patches now very 
powdery ; fungus spreading to controls. October 5. Perithecia in 
all stages of development—whitish, pale-green, and dark-brown in 
colour—now visible among the conidiophores on all three leaves. 
