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A TEXTBOOK OF THEORETICAL BOTANY 



Structure of the Gametophytes. 



The megaspore opens at the top and exposes a small, pale-green female 

 prothallus, which remains attached to the megaspore wall (Fig. 559). This 

 small mass of cells at first develops only one archegonium, and only if this 

 is unfertilized are more formed. Owing to the efficiency of the massula 

 arrangement, however, fertilization is usually promptly ensured. 



