Vegetative Nuclear Division in the Ascomycete <i>Ophiostoma fimbriata</i>

Abstract

Vegetative nuclear division in Ophiostoma fimbriata is not morphologically similar to ordinary mitosis. Nuclear division in this fungus is also different to that described in the vegetative mycelium of the related ascomycetes Neurospora crassa and Gelasinospora tetrasperma. In O. fimbriata the nucleolus is left out in the cytoplasm and does not divide together with the chromatin. Chromosomal complexes have been observed during the second vegetative division. These configurations do not appear to be aligned on a metaphase plate nor is there any visible evidence for the presence of a spindle.Added Note: Since the submission of this report further studies on the vegetative nuclei in O. fimbriata have revealed that towards the end of division the chromatin appears as an irregularly-shaped, double bar or strandlike configuration. Examples of such configurations are shown in Figs. 12 and 13, though in Fig. 12 they appear too densely stained to be properly resolved. At the end of division these strands, which lie almost parallel to each other, do not slide apart in opposite directions nor do they separate to “opposite poles”. They divide transversely at their midregions, usually one before the other, and then their extremities move apart in a manner comparable to that shown in Figs. 9, 15, and 30. A more detailed report describing the morphology and suggesting the significance of these configurations in a number of fungi is being prepared for publication at a later date.