Scurf
A condition often met with in Potato tubers, in which the surface shows clefts or slits, beneath which lie black masses of rotting tissue. Observation of the cause shows this to be, in part at least, the presence of superfluous moisture in the soil. This favours greatly the production of what are known as lenticels, or small groups of loosely-arranged cells below the stomata. These loose cells increase, and readily absorb water from the exterior. The swelling bursts the outer skin of the tuber, forming the slits, and giving still more free access to water. Cork is formed to repair the injury; but is also burst by increased growth of the lenticel, and is renewed to repair the injury as far as possible. The cells saturated with moisture begin to decay, and offer a favourable occasion of entrance to the spores of Fungi; hence, in a short time, the tissues below the slits become blackened and soft, the cells show Fungus threads, and the starch is removed from the neighbouring cells. Even where the actual amount of material destroyed is small, the unsightly appearance of the tubers frequently lessens the value of the crop. The best remedy is good drainage, together with efficient means to loosen the soil, and to permit free access of air.
The term "Scurf" is also applied to the loose, scaly matter on the epidermis.