In 1793 German theologist and naturalist Christian Konrad Sprengel issued Das entdeckte Geheimniss der Natur im Bau und in der Befruchtung der Blumen from Berlin through Friedrich Viewig dem aeltern, publishers. Sprengel's work, with its 25 plates engraved after drawings by the author, made a fundamental contribution to our understanding of the role insects play in plant fertilization, and is recognized as one of the founding works of what is now known as pollination or floral ecology.
Although J. G. Kölreuter had established the role of insects in the pollination of flowering plants in the 1760s, this phenomenon aroused little interest until nearly three decades later, when Sprengel, an amateur botanist, began observing the pollination of geraniums. After spending six years examining the relationship between flowers and their pollinating insects, Sprengel concluded that floral structure in entire orders of flowering plants can be interpreted only by analyzing the role of each part in relation to insect visits. He realized, as Kölreuter had not, that the entire structure of the flower was geared to this method of fertilization, and was the first to describe and illustrate, in nearly 500 species, the principal adaptive floral mechanisms concerned in pollination. In an important corollary, Sprengel noted the great frequency of dichogamy (the maturation at different rates of male and female organs in the same flower), and concluded that Nature did not intend any flower to be fertilized by its own pollen. Darwin recognized the importance of Sprengel’s work, which he read in 1841, and elaborated upon Sprengel’s observations in the Origin of Species (1859), Orchids (1862) and Cross and Self Fertilization (1876).
Dibner, Heralds of Science 30. Norman 1990. Nissen (botany) 1883. Morton, History of Botanical Science, pp. 326-328. 42702