THE MALE GAMETOPHYTE 133 



" prothallial " nucleus. This older view is the one given in 

 Goebel's Outlines of Classification and Special Morphology. In 

 1884 Strasburger 12 recognized the real nature of the two nuclei 

 and interchanged the names, applying them as they have been 

 used ever since. We have substituted the name " tube-nucleus "" 

 for " vegetative nucleus," not only because the development of 

 the tube is its most conspicuous function, but also because it is 





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 f *5 



e / 



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FIG. 62. Cypripedium spectabile. Section of microsporangium, showing microspores in 

 various stages of division into tube and generative nuclei ; although the divisions- 

 are nearly simultaneous throughout the microsporangium, it will he seen that in 

 some cases the nuclei are in the spirem stage, while in others the tube and genera- 

 tive nuclei are easily distinguished ; x 300. 



not the morphological equivalent of the vegetative or prothallial 

 cells of the Gymnosperms and heterosporous Pteridophytes. 



A generative cell is formed by the more or less distinct or- 

 ganization of the cytoplasm about the generative nucleus. This 

 cell usually lies free in the body of the spore, but is often cut 

 off by a distinct wall, as in Typha, (Schaffner 31 ), Sparganium 

 (Campbell 43 ), Xaias (Campbell 29 ), Convallaria (Wiegand 45 ), 

 Neottia (Guignard 9 ), Populus (Chamberlain 30 ), Asclepias 



