Many members the Polypodiaceae sensu lato show a conspicuous, yellow or white deposit on the lower surface their fronds. Therefore, they are often called gold ferns, gold-back ferns, silver ferns, or silver-back ferns. This is especially true for members the genus Pityrogramma Link. Such deposits also occur in Cheilanthes Swartz and Notholaena R. Br., although they are less known because species these genera are not easily cultivated in greenhouses. The culture the decorative species Pityrogramma was especially in fashion at the beginning the 19th century. Both P. calomelanos (L.) Link and P. chrysophylla (Swartz) Link were grown at Kew beginning in 1790. Fanciers were attracted by the great variability species and strains and by the formation various forms and hybrids that occurred during the culture of Gymnogramma. However, the proliferation hybrids and horticultural forms led to serious taxonomic confusion. Domin's (1929) statement is still valid: one can easily find completely different species or hybrids grown in greenhouses under the same name. Even recently in botanical gardens the name P. sulphurea (Swartz) Maxon has been applied to varieties P. chrysophylla and P. austroamericana Domin.
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Eckhard Wollenweber (1978) studied this question.