This illustration is an example of nature printing, which involves sandwiching the specimen between a polished steel and a lead plate and passing them through a roller press to leave an impression of the object in the lead plate. The lead plate can then be used as a printing plate or is more commonly electrotyped, whereby a copper layer is ‘grown’ onto a mould taken from the original, placed in a solution of copper sulphate with an electric current passed through it.
Although modelled on the actual plant, nature prints lack the illusion of three dimensions conveyed by a conventional illustration, and in fact resemble flattened herbarium specimens. The image was printed in two colours applied on the same plate, a method called à la poupée (named from the French word for doll after the small doll-shaped dabbers used to apply ink to the plate); the colours blend where they meet, rather than overlap and under a magnifier some of the leaves reveal a small amount of black ink over the green.
Henry Bradbury (1829–60) issued his first efforts in nature printing in 1854 as a volume 'showing the application of the art for the reproduction of botanical and other natural objects with a delicacy of detail and truthfulness unobtainable by any other known method of printing...' He had studied under Alois Auer (1813–69) at the Imperial Printing Office in Vienna and seen the technique used there.