THE SPRUCE FIR 



269 



within its winged membrane no less than five cells 

 are enclosed : first, the large cell, which still forms 

 the main part of the whole ; second and third, the two 

 little collapsed cells next the wall; fourth, the stalk- 



Fro. Ill . A, Pollen grain ofPicea excelsa shortly before it is 

 ripe, w, w, the wings ; 1, the large vegetative cell ; 

 its protoplasm is contracted ; n 1 , its nucleus ; 2, 3, the 

 two collapsed cells ; 4 and 5, the stalk-cell and terminal 

 or generative cell, not yet completely divided from one 

 another. B, Pollen-grain beginning to germinate. The 

 large cell, 1, is growing out to form the pollen-tube. 

 Lettering as before. C, Germination more advanced ; 

 only upper part of pollen-tube shown. The generative 

 cell, 5, has divided into two, each with a very large 

 nucleus. Magnified 240. (After Strasburger.) 



cell ; fifth, the terminal cell. We see, then, that the 

 pollen-grain of a Fir is a much more complicated 

 structure than that of an Angiosperm (see Fig. 111). 



