626 The American Naturalist. [ August, 
THE BACTERIAL DISEASES OF PLANTS: 
A CRITICAL REVIEW OF THE PRESENT STATE OF 
OUR KNOWLEDGE. 
By Erwin F. SMITH. 
I. 
It is scarcely fourteen years since Dr. Robert Hartig declared 
that there were no diseases of plants due to bacteria.’ Two 
years later Dr. Anton de Bary, unquestionably one of the most 
learned and critical botanists the world has ever known and 
the foremost student of cryptogamic plants, expressed the belief 
that bacterial diseases of plants were of rare occurrence, and 
suggested as a partial explanation the fact that the tissues of 
plants generally have an acid reaction.” In his Vorlesungen 
über Bacterien, published in 1885, he expresses much the same 
opinion,’ and cites only four diseases, viz., Wakker’s hyacinth 
disease, Burrill’s pear blight, Prillieux’s rose red disease of 
wheat grains, and the wet rot of potatoes, described by Reinke 
and Berthold. Concerning the first of these four diseases he 
says: “Successful infection experiments and exact study of the 
life history of the bacterium are still wanting.” Respecting 
the second he contents himself with briefly summarizing the 
statements made by Prof. Burrill. Of Prillieux’s micrococcus 
he says: “Its importance as a cause of disease cannot be 
determined with any certainty from the brief account. It 
1 «*Fiir die Krankheitsprocesse der Pflanzen kommen sie durchaus nicht in 
Frage, ete.” Hartig: (2) Lehrbuch der Baumkrankheiten, 1882, p. 27. 
2“ Bacteria parasitic on plants have scarcely ever been observed, a fact to 
which R. Hartig has already drawn attention. One reason for this may be that 
the parts of plants have usually an acid reaction.” De Bary: (2) Vergleichende 
Morphologie und Biologie der Pilze Mycetozen und Bacterien, 1884, p. 520 
English ed., p. 481. 
+“ According to the present state of our knowledge parasitic bacteria are of il 
little importance as the contagia of plant diseases. Most of the contagia of th 
numerous infectious diseases of plants belong to other animal and plant prepa: 
principally, as already noted, to the true fungi.” De Bary: (3) Vorlesungen 
ueber Bacterien, 1885, p. 136. i 
