The “Gloxinia” shown in this print is a representation of what was known at the time as Gloxinia rubra, the first cultivated red form of Sinningia speciosa. The original botanical publication (earlier the same year) and a reproduction of a later article which chronicles the collection of the red-flowered plant and the various and nefarious goings-on associated with it, are also available here.
The text associated with the article extols the beauty of this cultivar, and notes that it was available for purchase in limited supply, for one guinea per plant. In modern terms, using the consumer price index as the basis for calculation, that is about $120, high but not perhaps unreasonable. However, when calculated using other measures taking into account income inequality, the equivalent price could be well above four figures.
As in the original publication, this image shows the newly opened flowers having a much darker red color than the older ones. The text makes it clear that this was the actual pattern of color behavior with this collection.