384 BROOKLYN BOTANIC GARDEN MEMOIRS 



wheat readily passes over to certain species of Aegilops which some 

 systematists regard as a subgenus of Triticum. Aegilops aristata, Aeg. 

 Aucheri, Aeg. cylindrica, Aeg. ligiistica, Aeg. speltoides, Aeg. squarrosa, 

 Aeg. triaristata and Aeg. ventricosa proved very susceptible, while 

 Aeg. ovata and Aeg. triticoides gave negative results. 



It is evident that the powdery mildew of wheat can successfully 

 attack a very wide range of varieties belonging to the various species 

 of Triticum. It cannot, however, pass over onto Avena saliva, Hor- 

 deum vtdgare, Secale cereale and other grasses tested. 



The powdery mildew of rye has been tested out by the writer (no) ; 

 Secale cereale, S. anatolicum and S. montanum were readily infected, 

 S. dalmaticum proving resistant. This mildew will not pass over onto 

 any other cereal, nor such grasses as Bromus mollis, Dactylis glomerata, 

 Festuca elatior, Glyceria fluitans, Hordeum jubatum, Lolium perenne, 

 Phleum pratense and various species of Poa. 



Treboux (i6i) also states that conidia from Secale cereale infected 

 S. cereale but not Hordeum vulgar e nor Triticum vidgare. 



Salmon (128) reports meager data for the quack grass mildew; 

 conidia from Agropyron repens infected A. caninum and A. tenerum, 

 but not A. repens, A. acutum nor A. glaucum. 



Salmon (128) reports the successful infection of Poa annua, P. 

 nemoralis and P. pratensis with the mildew on the latter. The writer 

 (no) has successfully used the mildew on P. pratensis to infect P. 

 compressa, P. nemoralis, P. pratensis and P. trivialis. A number of 

 other grasses tested by these workers have given negative results. 



The powdery mildew of barley has been tested by both Salmon 

 (125) and the writer (117). According to the former the mildew from 

 Hordeum vidgare is readily transferred to H. decipiens, H. distichon, H. 

 hexastichon, H. intermedium, H. vidgare and H. zeocriton, while it is not 

 transferable to H. jubatum, H. murinum, H. secalinum nor H. sil- 

 vaticum; in addition H. bidbosum, H. maritimum generally gave nega- 

 tive results, infection occurring in only a few cases. The writer has 

 obtained positive results, using the mildew from H. vidgare, on H. 

 distichon, H. 7iudum, H. Steudelii X trifurcatum, H. tetrastichon, H. 

 trifurcatum, H. vtdgare and H. Zeocriton. Young seedlings of H. 

 nodosum also proved susceptible, although older plants gave negative 

 results. Negative results were obtained with H. bulbosum (except 

 that a few tufts of conidia were produced on one plant), H. maritimum 

 and H. jubatum. Efforts to transfer this mildew to various grasses, 

 including the other cereals, failed. 



Salmon (128) reports the successful infection of Dactylis glomerata 

 with conidia from the same host; negative results were obtained with 

 this mildew on Agropyron repens, Lolium temidentum and the cereals. 



