Insectivorous Plants was published by John Murray in July 1875. Darwin had been fascinated by carnivorous plants since 1860, when he observed sundews (Drosera) on a heath and was struck by the number of insects stuck to their leaves. “I care more about Drosera than the origin of all the species in the world,” he wrote to Charles Lyell — an exaggeration, but one that reflected the intensity of his interest.
The book is a model of experimental biology. Darwin subjected sundew leaves to an astonishing variety of substances — meat, milk, egg white, gelatin, urine, saliva, various acids and alkalis — to determine what triggered the plant’s digestive response. He discovered that the sundew’s tentacles were sensitive to extraordinarily small quantities of nitrogenous matter (he calculated that 1/20,000,000th of a grain of ammonium phosphate would cause a response) and that the plant secreted a digestive fluid similar to pepsin, the enzyme in the human stomach.
The implication was revolutionary: plants could do something that had been thought exclusive to animals — they could digest protein. The boundary between the animal and vegetable kingdoms, which had seemed absolute, was revealed as permeable. Darwin extended his investigation to Venus flytraps (Dionaea), butterworts (Pinguicula), and bladderworts (Utricularia), demonstrating that carnivory had evolved independently in multiple plant lineages.
Collecting Insectivorous Plants
First edition (John Murray, London, 1875): Green cloth binding.
Market values:
- First edition, fine: $1,000–$3,000
- Very good: $400–$1,000