Springer Online Journal Archives 1860-2000
Summary 1. Merosporangia are initiated as simple evaginations of the ampulla wall. As merosporangia elongate, two new wall layers are deposited. Plasmalemmasomes are associated with developing walls of both ampullase and merosporangia. 2. Apical vesicles are present in merosporangia at all stages of elongation. Similar vesicles, and cisternae sometimes containing material having the same stainability as vesicle contents, are present in the ampulla. 3. In merosporangia in mid cleavage, the cleavage apparatus consists of furrows extending into the protoplast. Furrows are bounded by a membrane continuous with the ampulla plasmalemma and contain a lining layer of either granular or continuous appearance according to fixation. 4. Delimited spore protoplasts are bounded by a plasmalemma derived in part from the merosporangium plasmalemma and in part from cleavage furrow bounding membranes and are surrounded by an investing layer derived from the cleavage furrow lining. 5. The spore wall is laid down between the plasmalemma and the investing layer which thickens as the wall develops. 6. As sporangial heads mature, spores round off and spore walls thicken, the innermost layer of the ampulla wall and merosporangium wall is broken down, a new wall is formed internal to the ampulla wall and, in some heads, a cross wall is formed in the sporangiophore.
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