Potato Scurf and Potato Scab. 
i ' 
1713 
which was of importance to the working out of an undescribed 
fungus. 
A decree was issued by the Minister of Agriculture of the 
Argentine Republic requiring a certificate from the Consulting 
Botanist of the Royal Agricultural Society of England as to 
the freedom from dodder of all pasture seeds imported from 
England, without which no such seeds would be allowed to 
enter the country. In accordance with this decree a consider- 
able number of samples have been examined and certified. 
The Laboratory, 
44 Central Hill, Norwood, S.E. 
William Carruthers. 
APPENDIX. 
Potato Scurf and Potato Scab. 
The cause of the scabbed appearance of potatoes has been 
a puzzle to investigators, chiefly because an appearance some- 
what similar to the true scab has been mistaken for it. 
Many potato tubers in good condition present a more or less 
regular peeling off of layers of the epidermis as shown in the 
accompanying illustration (Fig. 3, A). Though this appearance 
at first sight resembles the real scab, on careful observation it 
will be found to differ from it distinctly. The tissues between 
the small patches of the peeling epidermis are entirely normal ; 
they are smooth, even glossy, as in a perfectly clean and 
healthy potato. This appearance is frequent in potatoes, and 
none of the many varieties are entirely free from it. 
Potatoes cultivated under strict conditions of complete 
sterilisation develop the same appearance. The separated 
epidermal patches remain organically connected with the 
underlying tissues, though the margins dry and turn up. It 
must be remembered that the potato tuber is a branch. In 
the rapidly expanding tuber the epidermis is torn and the 
increasing intervening spaces are covered with a new epidermis. 
This shortened branch is enormously developed to store food, 
and as the increasing diameter of the stem of the potatoes above 
ground finds relief by linear fissures in the epidermis, so the 
epidermis of the roundish tubers breaks into oval or roundish 
patches. This is a normal operation, and is not due to disease 
or any other secondary agent. Plants adapt themselves to their 
place of growth and soil, and this may explain how some 
potatoes present no such appearance. To this normal peeling 
off of the skin we will give the name scurf to distinguish it 
from the true scab. In experiments with potatoes having the 
scurf, the fungi that have shown themselves under cultivation 
