i66 



MORPHOLOGY 



the wings, giving a midrib appearance. In general the gametophytes 



are monoecious. 



Antheridium. The antheridia appear very early in the history of the 

 gametophyte (fig. 392), being abundant even in the filamentous stage. 

 In the mature gametophyte they occur on the ventral surface in the older 

 part, among the rhizoids (fig. 391). No single type of development can 



FIG. 391. Gametophyte of Aspidium, looking at the ventral surface, which bears 

 the sex organs and rhizoids; just behind the notch is a group of archegonia, and at the 

 base of the thallus there are numerous antheridia. 



be given for all the antheridia of Filicineae, for they are as variable in 

 this regard as are the sporangia. The two extremes (Marattiaceae and 

 Polypodiaceae) will be given, with the understanding that the inter- 

 mediate families show intergrades. 



Marattiaceae. In the Marattiaceae there is the type of antheridium 

 development usual among eusporangiates. The outer cell following the 

 periclinal division of the superficial initial produces a wall consisting of 



