FORMATION AND DISCHARGE OF SECONDARY SPORIDIA OF THE BUNT FUNGUS, TILLETIA-FOETIDA

Secondary sporidial formation and discharge in Tilletia foetida were investigated using light- and electron-microscopy. Allantoid secondary sporidia developed asymmetrically at the tips of enteroblastic sterigmata. The hilar appendix consisted of a slight protrusion ca. 1.7 nm diam. The cell wall was thinner at the hilar appendix than elsewhere in the cell. A septum consisting of electron-dense material sandwiched between electron-transparent material, developed between the sterigma and sporidium. During sporidial discharge, the cell wall and septum abscised at the proximal margin of the dense material. On ejected sporidia, a patch of cell wall was absent at the hilar appendix. Cell wall generation occurred at the hilar end of sporidia after ejection but not at the tips of sterigmata. Just prior to sporidial discharge, a drop of liquid formed at the hilar appendix. These drops were removed with a microneedle and induced to evaporate and reform by shifting them between dry and humid atmospheres. The mechanism of sporidial discharge apparently involved the rapid movement of the drop from the hilar appendix to the sporidium.