INTRODUCTION. 9 



deut.^ The rusts had to be actually grown, and more diligent field 

 observations became necessary. Everywhere the utmost confusion 

 existed as to the distribution of cereal rusts on the different grasses, 

 and frequently even the particular species occurring on any of the dif- 

 ferent cereals was only a matter of inference. By way of a beginning 

 in clearing up these problems a series of inoculation experiments with 

 uredospores was inaugurated by the writer on September 15, 1893, 

 and carried on until February 1, 1891, the material used being taken 

 from outdoors and propagated in the greenhouse during the winter. 

 The results of these inoculations showed that the particular rust forms 

 employed would not infect any cereal but the one from which they 

 were taken, exceiit Uredo graniinis from wheat, which when used upon 

 barley i^roduced one rust spot (39, y>. 3). It was also found that a 

 uredo form found common on Kentucky blue grass would not infect 

 wheat nor oats.' The conclusion was then expressed that " these experi- 

 ments seem to show that the rusts of various cereals are probably 

 physiological species." At the time this work was done the writer was 

 not aware that Bolley had made some experiments of the same kind. 

 BoUey, however, reached no conclusion (10, p. 2G3). 



On March 1, 1894, the writer began work for this Department, con- 

 sequently the inoculation experiments just described were dropped 

 and were not resumed for nearly two years. In the meantime Eriks- 

 son, who in 1890 began experiments in the same line, published numer- 

 ous articles^ giving many results corresponding with those above 

 mentioned and with others which have not yet been published. In 

 some instances, however, the results difier. 



Specialized forms of cereal rusts. — The species hitherto known all 

 over northern Europe under the one name, Puccinia rubigo-vera (DC.) 

 Wint., have been separated by Eriksson and Hennings into two dis- 

 tinct species, i. e., F. (flumarnm (Schmidt) Eriks. and Heun. (the "yel- 

 low rust)," and P. disjiersa Eriks. and Henn. (the "brown rust") (30, 

 pp. 197, 198, 257, 258). Three rusts, therefore, attack wheat in Sweden, 

 the yellow rust bemg, it is said, the most common and destructive. So 

 far as known this yellow rust does not occur in America, but the brown 



' Swell ideas had already been expressed by the writer in Science, Vol. XIV, p. 63. 



i^On page 4 of the Kansas Agr. Expt. Sta. Bull. No. 46 it is stated that Uredo 

 graininis of oats would not infect orchard grass, but subsequent investigations have 

 shown that this grass is a common host for that rust. 



5 Eriksson, Jakob, Die Getreideroste, prepared in conjunction with Ernst Henniugs 

 and published originally in Swedish, comprises the details of Eriksson's investiga- 

 tions from 1890 to 1893. It did not reach America until the summer of 1896. The 

 principal results were given in Die HanptresuUate einer neuen Untersnchung ilber die 

 Getreideroste (Zeitschr. f. Ptiauzenkrank., 1894, Vol. IV, pp. 66-73, 140-142, 197-208). 

 The first part of this article appeared one month before the results obtained by 

 Hitchcock and the writer were published, but was not seen by them for some 

 time after. Ueber die Speciahsirung dcs Parasitismus bei den Getr eider ostpilzen {Ber. 

 d. Deutsch. Bot. Gp- , 1894, Vol. XII, pp. 292-331) gave the results of his further experi- 

 ments for 1894, and also references to the work of Hitchcock and the writer. Sub- 

 eeciuent to 1894 Eriksson's researches have been reported in various papers. 



