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Evidence for a Two-Layered Sheath on Germ Tubes of Three Species of Bipolaris. Robert C. Evans, Associate professor, Biology Department, Rutgers University, Camden, NJ 08102; Henry Stempen(2), and Peter Frasca(3). (2)Associate professor, Biology Department, Rutgers University, Camden, NJ 08102; (3)Research associate professor, Orthopedics Department, Jefferson Medical College, Philadelphia, PA 19107. Phytopathology 72:804-807. Accepted for publication 27 October 1981. Copyright 1982 The American Phytopathological Society. DOI: 10.1094/Phyto-72-804.

The hyphal sheath of Bipolaris maydis race T, as well as those of B. maydis race O, B. zeicola, and B. turcicum, were composed of two layers that were visualized by differential staining and light microscopy. The inner layer reacted with a wide variety of stains, but the outer layer was visualized only by negative staining. In B. maydis race T the inner layer first became visible at the tips of the conidia just prior to germination. Later, it formed a fibrous, spherical collar at the base of the germ tube and continued as a thin coating over the hyphal apex. However, once the germ tube became approximately as long as the conidium, this layer was no longer visible in the apical regions of the hypha. Although the sheath was evident in scanning electron micrographs, it was usually torn or closely appressed to the germ tube; the two sheath layers were not distinguishable by this technique regardless of the method of preparation.