Life Histories of Cereal Smuts. 69 



With the increase in our knowledge of the life histories of the cereal smuts, 

 it has been found necessary to split up some of the older collective species, 

 both on account of their morphological and physiological characters, into 

 several new species. Ustilago segetum (Bull.) Dittm. and U. carbo Tul. were 

 originally used to include several of the species occurring principally on wheat, 

 oats, and barley, and these names have now been discarded and replaced by 

 others. 



At first the old species U. segetum was split up by Jensen', in 1888, into 

 the following four races : — U. segetum, var. tritici; U. segetum, var. avenue; 

 U. segetum, var. hordei, form fiuda ; U. segetum, var. hordei, form tecta. 

 And he showed, at the same time, that the smuts occurring on wheat, oats, 

 and barley were only able to infect the particular cereal on which they grew. 

 Then in the same year Brefeld found that the loose smut of wheat and 

 barley did not produce conidia on germination, and that their spores were 

 incapable of infecting oats. On these grounds he constituted a species 

 U. hordei, Bref., for the forms occurring on wheat and barley. In 1890, 

 Rostrup^ named the form tecto, determined by Jensen, U. jensenii, Rostr., 

 because the spores produce a promycelium with conidia. 



And, finally, in the same year Kellerman and Swingle^ raised Jensen's 

 two forms on barley to the dignity of species, and named them respectively 

 U. nuda (Jens.), Kell. and Sw., and U. hordei (Pers.), Kell. and Sw., so that 

 Brefeld's U. hordei was spUt up into the three species now retained — U. tritici, 

 U. nuda, and U. hordei. 



The names that will be adopted in this work are the following : — 



U. avenae (Pers.) Jens. (1889) — forming conidia on germination. 



U. hordei (Pers.) Kell. and Sw. {18^0) = U. jensenii, Rostr. — forming 

 conidia on germination. 



U. nuda{Jens.) Kell. and Sw. (1890) — forming no conidia on germination. 



U. tritici (Pers.) Jens. (1890)= f/. hordei, Bref. (in part) — forming no 

 ■ conidia on germination. 



