322 



PLANT MORPHOLOGY 



Fig. 270. Cones of cycads. A, female cone of Cycas rcooluta, consisting of a loose rosette 

 of megasporophylls; B, male cones of Zamia skinneri; C, female cone of Zamia skinneri 

 with nearly ripe seeds. 



pteridophytes. There may be only one initial or a row or plate of several 

 initials. The initials divide transversely, the outer segments being the 

 primary wall cells and the inner ones the primary sporogenoiis cells. A 

 wall several layers in thickness is developed (Fig. 272). The tapetum is 

 cut off rather late, and so it is uncertain whether it is derived from the 



