
47 
A POTATO DISEASE. 
By H. MARSHALL WARD, D.Sce., &.R.S., Professor of Botany in the University of 
Cambridge.* 
I have for some time past had occasion to recognise here and 
there, in various parts of England, a potato disease which is not due 
to Phytophthora, and which has often been ascribed to bacteria. 
During the past two years my attention has been especially directed 
to testing its bacterial origin, and I am convinced it is not due to 
bacteria, but to a true hyphomycetous fungus. 
Without going so far as to say there is no bacterial disease of the 
potato, I wish to express the conviction that the alleged cases of 
such lately published are not convincing, and that a tendency exists 
to draw conclusions from imperfect evidence. 
I shall show that the way into the tuber is prepared for bacteria 
by fungus hyphae, and the open passages of destroyed vascular 
bundles afford them ample space. The disease I have studied has 
appeared in a more or less: epidemic form at least twice in my 
experience : it was very common two years ago, and this year has 
been abundant in various parts of England. Ina subsequent 
publication I shall show that it is common and wide-spread, and 
even known in some countries, though not adequately recognised. 
Symptoms.—The shoots turn yellow and die prematurely during 
the summer, and before the tubers are anything like full. The 
disease starts from below and not from the leaves. ‘The roots are few 
and poor, and soon rotaway. The tubers are few, do not mature, 
and often rot in the ground. The leaves turn yellow and wither on 
the stems, with the symptoms of premature wilting, and often 
remain long hanging on the yellowing, glassy-looking, but still 
living stems. 
In very mild cases these symptoms are not obvious, and supervene 
*Reprinted from Abstract of papers read at the British Association Meeting, 1898. 

