400 



STRUCTURE AND LIFE HISTORIES 



tudinal section is made of a mature ovule (Fig. 297), tlie 

 remainder of the nucellus appears only as a thin mem- 

 brane adhering to the outer surface of the prothallus, or 

 endosperm, as it is here called. When the Qgg fails to 

 become fertilized the gametophyte may protrude, develop 

 chlorophyll, and lead a brief, semi-independent existence. 



Fig. 297. — Photograph of a longitudinal section of an ovule of Macro- 

 zaniia Moorei. mi, micropyle; n.c, nucellar cap; a.r, archegonia (the 

 venters only showing) ; il, inner, hard layer, o.l, outer, fleshy layer of the 

 integument; g, gametophyte; p.c, pollen chamber. Enlarged from D, 

 Fig. 296. 



Several archegonia develop in the apical end, imbedded 

 in the tissue of the prothallus, and with their neck-canals 

 opening at the surface into a pollen-chamber (Fig. 297). 

 They resemble somewhat the archegonia of the lower orders 



