Ultrastructural Characteristics of Spore Germination in the Moss Dawsonia Superba

The spore wall of Dawsonia superba has characteristics that, in many respects, are similar to those of other mosses except for the exine, which is layered in Dawsonia. Imbibed spores have a well‐developed endoplasmic reticulum with dilated cisternae that are associated with vesicles at the periphery of the cell. Ribosomes on the surface of the vesicles suggest that many vesicles originate from the endoplasmic reticulum. Two types of protein storage bodies are observed: membrane bound protein bodies with a homogeneous matrix which gradually becomes vesicular, and densely stained and non‐membrane bound bodies consisting of crystalline arrays of fibrils. As in spores of higher plants, the protein reserves disappear during germination and may be converted to starch and other materials needed for development of the gametophyte.