Polypodium
See list of 2 species in this genusHybridization has been an important force in Polypodium. It has led to the formation of several allopolyploid species, including our P. virginianum (the hybrid-derived species from P. appalachianum and P. sibiricum Sipl.). Though hybridization continues to be an important source of confusion, variation within the species is the major hurdle to understanding the identity of our taxa. Collectors are encouraged to gather reproductive specimens so that spore condition can be observed (fertile vs. abortive). The species show monomorphic and slightly lustrous spores compared with the nothospecies, which has highly polymorphic and dull spores. Reference: Haufler et al. (1993b).
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1a. Sporangiasters more than 40 per sorus; scales of rhizome and petiole golden brown; spores smaller than 52 μm in diameter; leaflet apex usually pointed; leaf blades tending to be more triangular, widest near the base [Fig. 30]
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1b. Sporangiasters fewer than 40 per sorus; scales of rhizome and petiole golden brown with a dark brown central strip; spores larger than 58 μm in diameter; leaflet apex usually rounded; leaf blades tending to be more oblong, widest near the middle [Fig. 31]
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