16 INVESTIGATIONS OF RUSTS. 



Tablk I. — ( 'allure experiments ivilh black stem ruM of Agropyron and Elymus — Continued. 



a Pustules differ in color from the original. 



b Rust changes in appearance. 



The result.s of these experiments, considered in connection with those 

 recorded in Bulletin No. 16, Division of Vegetable Physiolog-y and 

 Patholog-y, U. S. Department of Agriculture, appear to establish two 

 things, viz, (1) that the forms of black stem rust on wheat, barley, 

 Ilordeum juhatum^ Agropyron teneriim^ A. richardsoni^ Elymus cana- 

 densis, and E. canadensis glaucifolius are identical, with the proba- 

 bilit}^ that those on Elymus virginicus, E. virginicus muticus, and 

 Holcus lanatus^'' should be included; (2) that the black stem rust of 

 Ag7x>pyron occidentale^ is physiologically distinct from anjr other.'' 



A very interesting phenomenon in these experiments was the change 

 in color and form of sorus of the rust produced by a transference to 

 another host. In some cases after a transfer the rust w^as scarce!}^ recog- 

 nized. The change of color was sometimes from a bright yellow to a 

 deep brown or orange, or the reverse. The uredo of Agro])yron tene- 

 r II III, for example, was often very yellow on the leaves, but changed to 

 brown when transferred to w heat. On the species of Elymus the rust 

 has a brown, wax}' appearance, and the teleutospores long remain cov- 

 ered by the epidermis of the host. 



"On January 5, 1900, quite successful infections on wheat were made with tlie 

 uredospores of black stem rust of this ho.«t. 



''Probal)ly the most correct name of this host, which is known also as Agropyron 

 spicaium and A. glaunn (See Hitchcock, "Note on Nomenclature," Science, vol. 

 17, pp. 827-828, May 2t^, -J03.) 



'The form on this host was described as a distinct species, named Piicrinia a(/ro}>yri, 

 by Ellis and Everhart, in Journal of Mycology, Vol. VII, p. 131, March 10, 1892, a 

 fact not noticed by the writer until after most of these experiments were made. 

 This species includes Mddium dernatidis D. C. according to Doctor Dietel, the proof 

 of relationship being the result of culture experiments. (Oesterr. Bot. Zeitschr., 

 No. 8, 1892.) 



