THE FIGHT WITH THE FUNGI 57 



SEEING IS BELIEVING 



It so happens that a Dutch lens grinder named Leeuwenhoek had invented 

 the microscope the latter part of the seventeenth century and now we could 

 see. Leeuwenhoek was a few years ahead of Jethro Tull, but not far enough 

 ahead so that Tull knew much of anything about a microscope. Some hundred 

 years after Leeuwenhoek described his microscope, an Italian, Fontana, in 

 1766, looked through it at diseased wheat leaves and found the microscopic 

 fungus which we today call Puccinia graminis. Fontana, however, did not con- 

 ceive that these microscopic bodies that he saw were the cause of wheat rust. 

 He got himself embroiled in another mix-up in causation. He decided that 

 the fungus bodies he saw were excrescences growing out of the diseased tissue. 

 Fontana thought that the rust disease was the cause of the fungus rather 

 than that fungus was the cause of the rust disease. This is a curious inversion 

 of reasoning as we look back on it from here, but it was not so strange to 

 Fontana. 



Ten years later, Tillet, the master of the French mint, who was an amateur 

 plant pathologist on the side, was working with another ancient disease of 

 wheat called smut. Tillet looked through Leeuwenhoek's microscope and dis- 

 covered the fungus of the wheat smut, but he also tended to look upon the 

 fungus as the result of the smut rather than the cause thereof. Later, however, 

 he changed his mind because he was actually able to take the small spores 

 of the fungus and mix them up with healthy wheat seed. Wheat so inoculated 

 came down with the disease. This is probably the earliest experimental produc- 

 tion of any disease, plant or animal, on record. We might pause for just a 

 second to note that this was almost an even one hundred years ahead of 

 Pasteur and his famous demonstration of anthrax in sheep, normally recorded 

 as the first demonstration of the germ causation of disease. Tillet's work, how- 

 ever, did not convince very many people; more people were inclined to con- 

 sider the fungus as an excrescence from diseased tissue rather than the cause 

 of disease. 



In 1844 when the potato blight was devastating the potato crops of Ireland, 

 Dr. Lindley, the well-known editor of the Gardener's Chronicle in London, 

 was writing that the fungus that he could find with his microscope on the 

 leaves of the diseased plants was an excrescence from diseased tissue and not 

 the cause thereof. Thereby, Dr. Lindley did a great disservice to the Irish. 

 If he had truly sensed the nature of the fungus that he found on the diseased 

 tissue, he might very well have solved the potato blight problem right then and 

 there. But enough of that for now. 



