The digital age has made it easy for us to identify plants and animals using selections from the millions of illustrations that are available on the Web. Accessing images of specimens was a much greater challenge in the Nineteenth Century, just when more and more people were becoming interested in Natural History and wanting to identify plants and animals they collected from the countryside, or the shore.
One solution to the need for illustration was the use of line drawings, or watercolours, that could be made into plates, printed and thus appear in books. A good example comes in the work of Philip Henry Gosse, who was both a scientist and an able artist, so knew exactly which features to portray. Other approaches used real specimens preserved in spirit, or by taxidermy, but these were only readily available in Museums and similar collections. Freshly-collected plants could be compared with those in herbaria, labelled collections of pressed and dried specimens, but these also were not widely available, although many amateurs made their own. However, they were dependent on the herbaria, and illustrations, of experts to ensure accurate identification. Mary Wyatt used herbarium specimens of seaweeds to allow the publication of a necessarily limited number of books to aid identification, while Bradbury and others extended this approach by pressing plants on to lead plates to make an impression. Each of the plates was then coated with copper and could be used to print many copies, some in monochrome and some using colour for even greater realism . Like illustrations made from engravings of other art work, these become available widely [2,3].
Of the many examples of Nature Printing, among the best known are the cyanotypes of Anna Atkins, the daughter of John George Children FRS, for whom she had earlier prepared 250 woodcuts of shells for his translation of a work by Lamarck, the original not being illustrated . Through her father, she had contacts with Herschel and thus the early development of cyanotypes in which chemicals are transformed by light to give a blue background, with the subject blocking the effect of light and appearing white. With her keen interest in illustration, Anna Atkins made cyanotypes of seaweeds that were then bound into a small number of volumes.
Complete collections of Anna Atkins cyanotypes have become justly famous – and very valuable. I was privileged to look through the large collection that was owned by Frederick John Horniman and is now held by the Horniman Museum in London. Each is printed on watermarked Whatman paper, mostly of 1846 and 1849 in the volumes that I saw, and all have a wonderful quality. As aids to identification, they give dimension and the arrangement of fronds of the seaweeds but no natural colour. One would be hard pressed to identify fresh specimens from some illustrations, especially of small algae, or those that are toughened with natural strengthening (see the images below for examples). Mounting specimens that were translucent meant that some surface, and internal, detail became visible and these cyanotypes are especially impressive.
Anna Atkins labelled each sheet with the Latin binomial of the seaweed and this would have been written in ink on strips of paper that were then cleared, most probably using highly refined oil. The labels could then be mounted with each alga and their outline is seen clearly in the prints at the Horniman Museum. Whatever their practical use, the Anna Atkins cyanotypes are beautiful works of art from Nature and it was a privilege to see them. Soon to be superseded by photography, they mark an exciting step in the Art – and Science - of Biological Illustration .
 Roderick Cave (2010) Impressions of Nature: A History of Nature Printing. London, The British Library.
 A. E. Gunther (1978) John George Children, F.R.S. (1777-1852) of the British Museum. Mineralogist and reluctant Keeper of Zoology. Bulletin of the British Museum (Natural History) 6: 75-108
I am grateful to Helen Williamson and the Horniman Museum for letting me see these valuable works and for allowing me to reproduce pictures of them in this blog post.
For those wanting to make cyanotypes of their own, a video explaining the technique can be found at: https://www.youtube.com/watch?v=gvvVUfdqDaM and I recommend Roderick Cave's brilliant book (reference  above) as an introduction to all aspects of Nature Printing.