Germination of Melampsora larici-populina uredospores on poplar leaves1

Using an electron scanning microscope the germination of Melampsora larici-populina ure dospores was observed on the lower leaf surfaces of a susceptible poplar clone Populus trichocarpa and a resistant one P. בSerotina de Poitou’. The observations were made from a few hours to more then a day after placing the uredospores on the leaf surfaces.