270 



Journal of Agricultural Research 



Vol. XIX. No 6 



Table III. — Temperatures at which infected wheat kernels were germinated 



Date of germina- 

 tion. 



Dec 



12, igi6 



Do 



Do 



Do 



Do 



Do 



Number 

 of plants 



21 

 20 

 20 



23 

 24 



24 



Temperatures. 



-2° C. alternated with 15° C 

 7° C. alternated with 15° C 



12° C. continuously 



2° C. alternated with 21° C. 

 10° C. alternated with 18° C 

 15° C. continuously 



Date of transfer 

 to greenhouse. 



Dec. 30, 1916. 

 Dec. 26, 1916. 



Do. 



Do. 



Do. 



Do. 



Experiment 5. — A number of writers have suggested the possibility 

 of rust infection taking place from spores on the surface of the seed. To 

 test this possibility, several fiats of wheat were sown with seed that had 

 been literally covered with viable urediniospores of stemrust. Preston 

 wheat (C. I. No. 3081) was used for this experiment. In all, about 200 

 plants were grown. No rust infection appeared upon any of them at any 

 time. 



FIELD EXPERIMENTS 



Experiment i. — In the spring of 191 6 rusted wheat from various 

 sources was sown in the field along with clean seed and rusted seed 

 treated with the modified hot-water treatment. These plots were 

 examined every few days from the first appearance of rust infection. 

 After June 27 the plants were examined every other day. Table IV 

 gives the methods employed and results obtained in the experiment. 



The groups of plots numbered i to 4, 5 to 9, 10 to 13, and 14 to 18 

 were grown in different locations on the University Farm at Madison, 

 Wis. 



Stemrust was noted upon Hordeum juhatum near two of the plots on 

 July 3, 12 days before it appeared upon the wheat in these plots.^ Infec- 

 tion also had been common upon adjacent barberries for some time 

 previously. It will be noted that the plants grown from badly rusted 

 samples of seed did not develop rust any earlier or any more severely 

 than those grown from clean seed or from rusted seed which had been 

 treated with the modified hot-water treatment. 



Recently the writer has had opportunity to consult the notes on an 

 unpublished experiment somewhat similar to field experiment No. i, as 

 described above. The work was done by E. C. Johnson, at that time Pa- 

 thologist in Charge of Cereal Disease Investigations in the Bureau of Plant 

 Industry, and carried on at the University Farm, St. Paul, Minn., in 191 2. 

 The experiment is described and results are given in Mr. Johnson's report, 

 a copy of which is on file in the Office of Cereal Investigations, Department 

 of Agriculture, Washington. D. C. 



1 By inoculating wheat plants in the greenhouse this was found to be Puccinia grammis trilici. 



