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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 
Fro. 391. Gametophyte of Asptdium, looking at the ventral surface, which beats 
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 
