14 INVESTIGATIONS OF EUSTS. 



at Stillwater and were of the crown rust type. After this date the 

 experiments were continued at the State University laboratories at 

 Lincoln, Nebr., all host plants then in use being transferred to that 

 place. On November 16 the crown rust was found, in the uredo stage, 

 on ArrJienatheruDi elatius on the State Universit}^ farm, and a rusted 

 plant was transferred to the greenhouse. On December 11 inoculations 

 with the rust were made on oats and rye, resulting in a good infection 

 of the former in twelve days, but with no result on the latter. Fur- 

 ther ino'culations of oats with the Phalaris rust on February 16, 1898, 

 resulted again in a good infection in 9 days. 



No species of Rhamnus is native near Lincoln, Nebr., but lihamnus 

 lanceolata is rather common at AVeeping Water, about 20 miles east of 

 Lincoln, where it is often badly rusted with ^Fcidium. From that 

 place a large amount of the /Ecidium was obtained fresh on June 1, 

 1898. A water-drop culture of the material, made the next day, gave 

 a profuse germination of the spores in twenty-two hours. Inocula- 

 tions with the fficidiospores on oats and PJialaris caroliniana were 

 made June 1 and June 2, resulting in a successful infection of Phalaris 

 on June 14 and of oats on June 18. The oat inoculations were made 

 simply on detached portions of the plant preserved with their broken 

 ends in water in a damp chamber. As in all other instances, these 

 inoculations were made with the greatest of care to prevent accidental 

 infections. The whole series of experiments proves (1) the connection 

 of the aecidial form of Rhamnus with the crown rust of oats, and (2) the 

 identit}^ of the latter with the forms on Phalaris caroliniana and 

 Arrhenatherum elatius, besides making it probable that orchard grass 

 may also support this species. 



SEGREGATION OF HOST PLANTS. 



The most important economic results of the study of rusts are likely 

 to be derived from the investigation of the relationship of the forms on 

 our common grasses. Such work has alreadv been carried on to some 

 extent by the writer and partially reported in the l)ulletin entitled 

 "Cereal Rusts of the United States." A more detailed account of 

 some of this work will he given here. Because bearing upon the same 

 question, it seems proper to mention also some experiments with the 

 rusts of Salix and Populus. Probably the greatest confusion exists 

 concerning the identity of the different forms on Agropyron and 

 Elynms, though there is much uncertainty also about those occurring 

 on Bromus and other genera. 



The experiments here described were conducted at Stillwater, Okla.. 

 Manhattan, Kans., Lincoln, Nebr., and Washington, D. C, the host 

 plants being sometimes transferred from one place to another. Of all 

 these rusts the one receiving most attention was the black stem rust 

 of Agropyron and Elymus. 



