Abstract
1. The results of the inoculation experiment with uredospores of Puccinia triticina ERIKS. on barley show that seedlings of 13 varieties tested are susceptible in summer and autumn.
2. The uredosori on barley seedlings are fewer in numder and smaller in size than those on the susceptible wheat plant. But the pathogenicity of the uredospores produced on barley is not changed and they can infect barley and wheat again.
3. In the course of winter, these barley seedlings show a high degree of resistance against the fungus.
4. When inoculated in winter, the germ tubes enter the leaves freely through the stomata, but some of the infecting hyphae stop their growth, producing haustrium mother cells, without forming haustoria and these hyphae soon die. The wall of the host cells in contact with this dead hyphae is swollen and deeply stained with safranin. Occasionally some haustoria are developed, but sooner or later they collapse and die together with the invaded cells.
