REED: SPECIALIZATION OF PARASITIC FUNGI 



385 



Salmon (123, 126, 127) has made extensive tests with the mildew 

 on the brome grasses using conidia from a number of different species. 

 Some of Salmon's more important results are indicated in the following 

 table : 



From his data, Salmon concluded that four, or possibly even five, 

 specialized races exist within this genus. In looking over his data, 

 however, there seems to be very little, if any, difference between some 

 of them. The races on B. interruptus and B. hordeaceus dififer only 

 in their capacity for infecting B. commutatus, the mildew on B. horde- 

 aceus infecting this host, while that on B. interruptus does not. The 

 race on B. commutatus differs from that on B. hordeaceus in not in- 

 fecting B. mollis and B. interruptus. The race on B. arveyisis infects 

 this same species but not B. mollis. Finally the race on B. tec tor um 

 differs from that on B. hordeaceus in being able to infect B. sterilis. 

 It is evident that these races are not distinctly marked off from one 

 another. 



But little work has been done using ascospores from various hosts. 

 Marchal (98) mentions the following results: (i) ascospores from 

 Hordeum vidgare infected H. vulgare, H. distichon, H. trifurcatum and 

 //. Zeocriton, but not Avena sativa, Secale cereale nor Triticum vulgar e; 

 (2) ascospores from Secale cereale infected 5. cereale, but not Hordeum 

 vulgare nor Triticum vulgare; (3) ascospores from Triticum vulgare 

 infected T. vulgare but not Agropyron caninum, Avena sativa, Hordeum. 

 vidgare nor Secale cereale. Salmon (124, 132) found that ascospores 

 from Hordeum vulgare infected 77. vulgare, H. trifurcatum and 77. 

 Zeocriton, but not 77. bulbosum, H. jubatum, 77. maritimum, 77. secali- 

 num, Avena sativa, Secale cereale nor Triticum vulgare; ascospores from 

 Bromus commutatus infected B. commutatus and B. hordeaceus, but not 



'" The denominator indicates the number of leaves inoculated, the numerator 

 indicates the number infected. 

 1^ Subinfection. 



