Figs. 208-210.—Black rust of wheat, showing sori of teleutospores.
401. Wheat rust (Puccinia graminis).—The wheat rust is one of the best known of these fungi, since a great deal of study has been given to it. One form of the plant occurs in long reddish-brown or reddish pustules, and is known as the “red-rust” ([figs. 206, 207]). Another form occurs in elongated black pustules, and this form is the one known as the “black rust” ([figs. 208]-[211]). These two forms occur on the stems, blades, etc., of the wheat, also on oats, rye, and some of the grasses.
Fig. 211.
Head of wheat showing
black rust spots on
the chaff and awns.
Fig. 212.
Teleutospores of wheat
rust, showing two cells
and the pedicel.
Fig. 213.
Uredospores of wheat
rust, one showing
remnants of the
pedicel.
402. Teleutospores of the black rust form.—If we scrape off some portion of one of the black pustules (sori), tease it out in water on a slide, and examine with a microscope, we see numerous gonidia, composed of two cells, and having thick, brownish walls as shown in [fig. 212]. Usually there is a slender brownish stalk on one end. These gonidia are called teleutospores. They are somewhat oblong or elliptical, a little constricted where the septum separates the two cells, and the end cell varies from ovate to rounded. The mycelium of the fungus courses between the cells, just as is found in the case of the carnation rust, which belongs to the same family ([see Parag. 186]).
