20 CEREAL RUSTS OF THE UNITED .STATES. 



Tablk 2. — Inoculation exjjeriments tvith Uredo ruhujo-rera of nheat. 



Date of 

 inoculation. 



Place where experi- 

 ments were made. 



' Origin of ! 

 inoculating 

 I material. ' 



Plant inoculated. 



Jan. 19, 1897 I Washington, D. C... 



Do do 



Do do 



Feb. 1,1897 do 



Do do 



Do do 



Do do 



Feb. 12, 1897 I do 



Do I do 



Do ' do 



Feb. 13. 1897. . . . | do 



Do ■' do 



Feb. 24, 1897.... I do 



Wheat. 



do. 



do . 



do . 



do. 



do. 



do. 



do . 



do. 



do . 



do . 



do . 



do . 



Period 

 of incu- 

 bation 

 (days). 



Wheat 



Missogen wheat 



Rve 



Wheat 



Rye 



Barley 



Oats.'. 



Wheat 



Taganrog wheat 



Missogen wheat 



Wheat 



Dactylis glome rata 



Akavemidashi wheat 



Do 



Feb. 11, 1898'..- 

 Do 



Do. 

 Do. 

 Do. 

 Do. 

 Do. 

 Do. 



do 



Lincoln, Xebr. 

 do 



do 

 .do 

 do 

 do 

 .do 

 .do 



-do 

 -do 

 .do 



-do 

 .do 

 .do 

 -do 

 -do 

 .do 



California white wheat 



Elymus canadensis 



Elyinus canadensis glauci- 

 folius. 



Elymus virginicus , 



Agropyron richardsoni .... 



Agropyron spicattiiii 



Agrcpjiron tenerum 



Dactylis glomeruta 



Panicum autumnale : 



Result. 



8 



8 

 8 

 8 

 11 

 11 

 11 

 15 

 15 

 11 



11 

 13 



7 



13 

 13 

 13 

 13 

 13 

 13 



Successful. 

 Negative. 



"Do. 

 Successful. 

 Negative. 



Do. 



Do. 

 Successful. 



Do. 



Do. 



Do. 

 "Negative. 

 Only one or 

 two spots. 



Do. 

 Negative. 

 Doubtful. 



Do. 

 Negative. 

 Do. 

 Do. 

 Do. 

 Do. 



' Through inadvertence no check experiment was made. 



Two of the experiments were doubtful ou account of the slight infec- 

 tions, which were ijossibly accidental. Although under date of Febru- 

 ary 11, 1898, no check experiment of inoculations from wheat to wheat 

 was made, in numerous other exi)erimeiits with wheat alone the inoc- 

 ulations never failed to infect readily, where ordinary cultivated varie- 

 ties of Triticum vulgare were used.^ 



Although the experiments carried on with Uredo ruhigo-vera were 

 not so numerous as those made with other rusts, they are nevertheless 

 sufficient to show that the limits of this rust form are quite closely cir- 

 cumscribed by physiological conditions. Many more experiments with 

 this rust would have been made during the winter of 1896-97 had it 

 not been for the presence of wheat mildew, which tended to vitiate all 

 work and which could not be got rid of without interfering with the 

 experiments. 



The time of incubation, or the interval between inoculation and 

 appearance of rust in the case of Credo nibigo-vera of both wheat and 

 rye, is somewhat longer, as a rule, than that of the other cereal rusts, 

 ranging under usual conditions in the greenhouse from seven to ten 

 days. 



The experiments so far made indicate that only varieties of the fol- 

 lowing species and subspecies^ of the genus Triticum act as hosts for 



• A fact of interest in this connection is that in one experiment Missogen, a hard 

 ■wheat, of the snbspecies Triticum durum, from Greece, showed no infection. Althongh 

 this may not seem very significant at first, yet if considered in connection with facts 

 shown in Table 8, it "will be found to be in accord with the results of experiments on 

 rust resistance of varieties given in Table 3, which show that durum and poulard 

 ■wheats are more resi-stant to orange leaf rust than are the bread wheats. 



■2 The classification of wheats followed in this bulletin is that of Koeruicke and 

 Werner (44). 



