PTERIDOPHYTES 



147 



numerous mother cells, in each of which a tetrad of spores 

 is formed. The disorganization of the walls of the mother 



FIG. 127. The ostrich fern(0nodea stntthiopteris), showing differentiation of foliage 

 leaf (a) and sporophyll (6). After MARION SATTERLKB. 



cells sets the spores free in the cavity of the sporangium, 

 and ready for discharge. 



