Fig. 10. — SilpMum integrifolium. Longitudinal sections of microsporangia ; x 520. 

 A, single row of archesporial cells ; in two cells division into primary sporogenous 

 and primary parietal cells has already taken place, fi, sporogenous and tapetal cells 

 sharply differentiated. C, later stage showing spore mother-cells in synapsis. 2>, 

 a tetrad ("only three microspores shown) formed within the spore mother-cell. — After 

 Merrell.* 8 



85 



