A stress-induced “mycosome”phase of Aureobasidium pullulans consisting of minute reproductive propagules that may revert directly to walled yeast cells is described. Mycosomes detected by light- and electronmicroscopy reproduce within senescent plant plastids, and display three developmental pathways: wall-less cells (protoplasts), yeast cells, or membrane-bounded spherules that harbor plastids. Widespread in plant and algal cells, mycosomes are produced by both ascomycete and basidiomycete fungi
