116 BORTHWICK—WARTY DISEASE OF POTATO. 
“ The diseased potatoes were grown in 1906, on a piece of large 
“garden ground at-Kennet Village, the property of Lord Balfour 
“of Burleigh, in the County of Clackmannan, the area of the 
“ground being about 24 poles in extent. The kinds of potatoes 
“grown were British Queen, Up-to-Dates, Scottish Triumph, 
“ Herd Laddie, and Princess May Kidney. The whole crop was 
“damaged to the extent that they could not be used. They were 
“quite useless, the early varieties being, if anything, worse than 
“the late—especially the early Kidneys. The disease was first 
‘noticed when the new potatoes began to form. It first appeared 
‘on the stems as a greenish-looking canker, which attacked the 
“tubers as they grew and soon made them into a mass of 
“corruption. The ground on which the diseased potatoes grew 
“is the ordinary black garden soil about 15 inches deep, resting on 
“clayey till. The surface soil seems to be a good deal mixed 
“with furnace ashes, and does not appear to be very pure black 
“soil. The same ground was planted with potatoes in 1905, and 
“there was no disease then, or at least, if there was, it had been 
“so slight that it had not been taken notice of. It is said that 
“the disease was noticed in a few of the neighbouring gardens 
“in 1906, but if it did exist it was only very slightly. The 
“dwelling-house in connection with this piece of ground was 
“partly rebuilt in 1905-06, and some of the lime rubbish from 
“the building was spread on part of this ground. The part on 
“which the rubbish was put was the worst part with the 
“ disease.” 
Examination of the tuber showed that sometimes only a few 
localised warty excrescences, or again the whole potato, was 
converted into a coral-like mass. Figs. 12 to 18 show the general 
appearance of the malady. The excrescences are the result of 
the irritation caused by a parasitic fungus which inhabits the 
parenchyma-cells.near the surface. | 
On examining the tissues microscopically, numerous resting 
spores were to be seen in the infested parts. They occurred most. 
abundantly in the outer layers—see Fig. 8, which is a photo- 
micrograph of a median longitudinal section, also Fig. 11, which 
is a small portion photographed under a higher magnification 
while Figs. 7 and 10 are low and high-power photomicrographs 
of surface sections. In this condition of spores the fungus passes 
