Taxonomic Controversy
Taxonomic classification within the genus Cystopteris is complex. Within a year of Sim's publication Thomas Moore stated his view was that, on balance, Dickie's Bladder-fern was a variety of C. fragilis. Various opinions have been published over the intervening years, with a consensus that C. dickeana was a separate species emerging in the 1930s, although recent research suggests that Moore's caution may have been appropriate. C. dickeana has broader, less divided and more closely spaced pinnae than C. fragilis and the spores of the former are typically wrinkled and ridged rather than the spiny form of the latter's. However, there are significant variations within the populations of both forms and these characteristics are by no means fixed. On the other hand there is also evidence that crosses of the two types produce sterile hybrids.
The treatment of Cystopteris in the Flora of North America (1993) regards Cystopteris dickieana as a synonym of Cystopteris fragilis.
Read more about this topic: Cystopteris Dickieana
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