Entry From
Flora of North America, Vol 2,
Discussion
Polypodium saximontanum is an allotetraploid species whose progenitor diploid species are P . amorphum and P . sibiricum (M. D. Windham 1993). Prior to its recognition as a distinct species, collections of P . saximontanum were variously referred to P . montense F. A. Lang (= P . amorphum ), P . hesperium , and/or P . virginianum . In addition to its separate geographic range, P . saximontanum can be distinguished from P . virginianum by having narrower leaves and a reduced frequency of glandular hairs on its sporangiasters. Polypodium saximontanum also has a separate range from P . amorphum and has spores with large (greater than 3 µm tall) projections. Although P . saximontanum overlaps in range with P . hesperium , the latter species has no sporangiasters. Tetraploid hybrids of these two species have misshapen spores.