382 BROOKLYN BOTANIC GARDEN MEMOIRS 



5. Poae upon Poa annua, P. trivialis, P. pratensis, P. caesia, P. 



miitalensis, P. nemoralis and P. serotina. 



6. Agropyri upon Agropyron. 



7. Bromi upon various species of Bromus. 



Salmon (123, 128) has infected Avena nuda, A. brevis and A. sativa 

 with conidia from A. mida; conidia from A. sterilis infected A. pratense 

 and A. sativa; and conidia from A. sativa infected A. sativa, A. brevis, 

 A. nuda, A. orientalis, A. sterilis and A. strigosa. Attempts to infect 

 twelve other grasses, belonging to different genera, with the oat mildew 

 failed. 



The writer (120) has carried out an extensive series of experiments 

 with the powdery mildew on Avena sativa. Infection occurred on the 

 following: A. barbata, A. brevis, A. fatua, A. Jatua var. glabrata, A. 

 ludoviciana, A. nuda, A. nuda var. chinensis, A. nuda var. elegantissima 

 A. planiculmis, A. pratensis, A. pubescens, A. purpurea, A. sativa 

 (sixteen varieties), A. sativa orientalis (six varieties), A. sterilis, A. 

 strigosa and A. sulcata. In most cases, in a large number of trials, 

 one hundred percent of infection was secured. The oat mildew also 

 infected Arrhenatherum avenaceum. Negative results were obtained 

 with Avena bromoides and A. sempervirens, as well as grasses belonging 

 to other genera. This race, then, extends over a wide range of species 

 and varieties of Avena, but, with the exception of Arrhenatherum 

 avenaceum, is restricted to this genus. 



Salmon (123, 132) has reported only a few results with the powdery 

 mildew of wheat. He successfully infected Triticum vulgare and T. 

 Spelta with conidia from the former. He also states that young 

 seedlings of Hordeum silvaticum could be infected with the same 

 mildew. 



Vavilov (164) has tested out, under field conditions, seven hundred 

 and fifty-five "pure-lines" belonging to the different species and 

 varieties of Triticum. He used pure lines belonging to thirty varieties 

 of Triticum vulgare, seven of T. compactum, ten of T. turgidum, nine 

 of T. Spelta, fifteen of T. durum, three of T. polonicum, five of T. 

 dicoccum and four of T. monococcum. In general the pure lines be- 

 longing to the different varieties of T. vidgare, T. compactum and 

 T. Spelta are extremely susceptible to the mildew, while the pure 

 lines of the varieties of T. durum, T. turgidum, T. polonicum and 

 T. monococcum proved, in the main, to be quite resistant. The pure 

 lines of some varieties of T. dicoccum proved to be highly susceptible, 

 while the pure lines of other varieties were markedly resistant. Dif- 

 ferences in the susceptibility of the pure lines were noted and certain 

 varieties, notably T. vulgare var. fuliginosum and T. dicoccum var. 

 picnurum stood out as distinctly immune. However, the pure lines 



