We have studied in Selaginella that two types of spores are present. One is smaller in size called micro spore and the other bigger in size called megaspore. This type condition is known as Heterospory. These spores have different functions to perform. Instead of growing into a gametophyte of similar structure, the heteros porous plants produce two different gametophytes. Micro spore grows into a sperm forming gametophyte. The other kind mega spore, grows into egg forming gametophyte. The two kind of spores are formed in two different kinds of sporangia. These like the sporangia of club mosses, horse tails and ferns have become protected as a result of the evolution of various enveloping structure.
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