Centriolar plaque and spindle microtubules in the ascomyceteSordaria humana

Centriolar plaque and spindle microtubules in young asci of an ascomycete,Sordaria humana were studied by electron microscopy. Centriolar plaque is electron opaque and has an amorphous structure. Two dispositions of centriolar plaque were observed, one entirely contiguous to the nuclear envelope in a meiotic division and the other partially joined to the envelope in a mitotic division following meiosis. The spindle was formed inside the nuclear envelope and spindle microtubules terminated at the polar protrusion of the nuclear envelope. Some spindle microtubules seem to connect directly with the centriolar plaque passing through perforations of the nuclear envelope.