406 



PART IV. CLASSIFICATION. 



sporangium, and this is followed by cell-formation. In the Angio- 

 sperms the cell-formation is simple, consisting in the aggregation 

 of protoplasm round one of the two nuclei, without any formation 

 of cell-wall, so that a small primordial cell, the generative cell, is 

 formed, floating freely in the protoplasm of the microspore which, 

 with the other nucleus, constitutes the vegetative cell. In the 

 Gymnosperms the process is rather more complicated. In the 

 simplest case (e.g. the Yew), the microspore divides into two cells, 

 separated by a cell- wall ; of these the one, the antheridial cell, 

 undergoes division into two, a stalk-cell, and a generative cell ; 



whilst the other remains as an undivided vegetative cell. In some 

 cases, however (e.g. Larch, Ginkgo, Fir), generally three cells are 

 successively cut off by parallel septa (Fig. 240) : of these the two 

 first formed are merely vegetative cells, and undergo disorgani- 

 sation, whilst the last is the antheridial cell, and undergoes 

 division into a generative cell and a stalk-cell. 



