In 1876 the German seed company Haage & Schmidt released a series of Zinnia hybrids they called Zinnia Darwini. These were the result of a cross between Z. haageana and Z. violacea (Z. elegans at the time). From the account in the 1877 edition of Cultivated Plants: their propagation and improvement By Frederick William Thomas Burbridge, the cross may have originally taken place in 1864 in France, initial selections made there and fine tuned by Haage & Schmidt prior to release. Below is a clipping of this account:
More complete descriptions were made in both English and German periodicals of that time. Many include pictures that were released by Haage & Schmidt. This English release was in The Florist and Pomologist in February 1876. Clippings of this account are shown below:
A more comprehensive description in the 1876 German magazine Deutsches Magazin für Garten- und Blumenkunde also included more pictures. I have not translated this article, but it looks to contain descriptions of the various colors the different strains included. Here is the clipping from the magazine:
