pETHYBKlDGfc; AND MuuPHv — Bacterial Dkease of the Potato. 8 



in 1896 by Erwin F. Smith (25) as occurring in the United States of America. 

 Smith's work leaves no room for doubt as to the real cause of the malady in 

 this case, it being due to a hitherto undeseribed organism to which he gave 

 the name of Bacillus solanaceanmi. The disease is characterized by the sudden 

 wilting of the foliage, and later on by a shrivelling and turning black of the 

 stems, the organism proceeding from above downwards, and ultimately reaching 

 the tubers underground through their rhizomes, and causing a brown or black 

 rot in them. B. solanacearum Smith is an organism which does not liquefy 

 gelatine, or " at most (?) does so very feebly, and not until after five or six 

 weeks." It produces a brown colouration when grown in nutrient agar, and 

 has a tendency to produce a zoogloea and a pellicle in the upper layers of 

 broth and peptone water. This organism does not appear with certainty to 

 have been met with up to the present by any observers working in Europe. 



In Germany a potato disease known as " Schwarzbeinigkeit " or 

 " Stengelfaule " was first made the subject of investigation by Frank (14) in 

 1899. This "Black-leg" or "Stem-rot " is characterized as follows : — In the 

 spring, soon after the potato plants have come up and the stalks are about a 

 foot high, indi^ddual plants here and there are seen to become sickly and to 

 die, whilst the portion of the stem beneath ground, and sometimes part of it 

 just above the soil-level, is found to be black and rotten. The consequence is 

 that growth is stopped, the foliage becomes gradually wilted and yellow, and 

 the whole plant dries up aad becomes dead. Fungus mycelium and bacteria 

 are to be found in the decaying stalks, and they advance from below upwards, 

 carrying the rot with them. An organism, which he named Micrococcus 

 phytopMliorus, and which he had found to be the cause of rotting in potato 

 tubers, was found by Frank constantly associated with the rotten stalks of 

 these potato plants. This organism was isolated and obtained in pure culture, 

 and with it Frank succeeded in inoculating cut stalks of the living potato 

 plant, and in producing the symptoms of rot in them. He does not appear to 

 have attempted the inoculation of potato plants growing in the soil ; never- 

 theless there is little doubt but that Frank was dealing with an organism 

 really pathogenic to the potato-plant, and responsible for the disease named. 



Iwano£f(19) described in 1899 a bacterial disease of potato-stalks which 

 he had observed on a somewhat large scale during the previous year in the 

 iieighbourhood of St. Petersburg. The trouble was confined to the portions 

 of the plants above ground, and did not pass to the tubers. Bacteria were 

 abundant in the diseased tissues ; and two kinds were isolated, neither of which, 

 however, proved to be pathogenic. Infection experiments with the dead 

 bacteria-containing cells from the diseased tissues introduced into healthy 

 stems succeeded. Although lie did not succeed in isolating a pathogenic 



