114 
Ernest S. Salmon. 
E. Cichoracearum on P. major is a “ biologic form ” probably 
specialized to species of the genus Plantago. When sown on P. 
media the result is sometimes full infection, while sometimes the 
conidia fail entirely to produce any infection. In one case where 
infection resulted, the fungus produced, after a crop of conidia, a 
mature perithecium. This is the first instance recorded of the 
formation of perithecia by a fungus transferred from one host- 
species to another. We have, it seems, in the present case, an 
instance of a fungus which has, so to speak, advanced half-way in 
the process of becoming specialized to a single species of host- 
plant—in the present case, P. major; it is unable apparently to 
infect P. lanceolata, but it can still occasionally fully infect P. 
media, and produce perithecia on this species. 
The Oidium of E. Galeopsidis on Ballota nigra (Table 9) proved 
unable to infect Salvia verticillata and Leonnrus Cardiaca. 
TABLE I. 
Infection-experiments with conidia of E. Graminis on Avena sterilis. 
Kxper. 
No. 
Date, 
1903 . 
Species used as Host. 
‘ 
No. of 
leavesino¬ 
culated. 
No. of 
leaves 
infected. 
76a 
Aug. 2 
Avena sativa 
3 
3 
93a 
„ 13 
• • • yy ... 
3 
3 
76f 
„ 2 
A. pratensis 
3 
1 
76g 
„ 2 
• • • n • r 
3 
0 
93b 
„ 13 
••• n 
3 
0 
76b 
„ 2 
A rrhenatherum avenaceum 
3 
0 
76c 
„ 2 
• •• 11 • • • 
4 
0 
93c 
„ 13 
• • • M • • • 
3 
0 
76d 
„ 2 
Lolium temulentum 
6 
0 
76 h 
„ 2 
Festuca elatior 
r* 
O 
0 
76i 
„ 2 
Bromus unioloides 
4 
0 
76j 
„ 2 
... B. sterilis 
3 
0 
Remarks. 
76a. August 7. The inoculated leaves with numerous nearly 
powdery Oidium- patches; controls free. August 20. All three 
leaves with powdery patches of Oidium ; fungus spreading to 
controls. 
93a. August 21. Powdery patches of Oidium on the three 
inoculated leaves; controls free. August 26. The three leaves 
covered with very powdery Oidium- patches; fungus spreading to 
controls. 
76f. “ Subinfection ” only. August 7. A very few scattered 
conidiophores on one of the inoculated leaves; controls free. 
