Abstract
The fine structure of Japanese pear leaves infected with Gymnosporangium haraeanum Sydow was investigated. Sporidia penetrated the cuticle of epidermal cells and formed intracellular hyphae enveloped by poorly-developed, thin layers.
The hyphae elongated towards palisade parenchymatous cells and formed other intracellular hyphae in these cells. Intracellular hyphae in palisade parenchymatous cells were surrounded by thin electron-translucent layers and frequently became multicellular. The intercellular hyphae invaded the palisade and spongy parenchyma cells and formed intracellular hyphae.
