During his lifetime, his work was somewhat neglected, not only because it seemed to a lot of his contemporaries as obscene that flowers had something to do with sexual functions, but also because the immanent importance of his findings on the aspects of selection and evolution was not recognized. One contemporary A. W. Henschel in Breslau (1820) wrote that Sprengel's idea gave the impression of a fairy tale to entertain a schoolboy. It did get a favourable review from his doctor Heim who wrote that the "work is a masterpiece, an original of which all of Germany can be proud" of. The director of Botanical Garden in Göttingen Georg Franz Hoffmann also noted that he had verified some of the observations. Charles Darwin was introduced to Sprengel's book by Robert Brown. Darwin recognized Sprengel and noted that ""he clearly proved by innumerable observations how essential a part insects play in the fertilization of many plants. But he was in advance of his age."" Darwin was impressed by Sprengel's approach and it inspired him in his own studies that led to the "On the various contrivances by which British and foreign orchids are fertilised by insects, and on the good effects of intercrossing" (1862) where he came up with the conclusion that nature "abhors perpetual self-fertilization".