32 Diseases of the Potatoe. 
terior has lost its brightness as well as its moisture and 
whiteness. The starch grains gradually disappear, and cells 
filled with air, and a yellow fluid, occupy their place. Many 
cells are torn, and the passages are filled with a brown fluid. 
Scattered between the cells in all directions will be found 
dark colored, opaque grains of various forms and sizes. These 
grains do not develope any further, but at last burst, and in 
their appearance and history resemble the Protomyces, or 
primitive fungus germs of unger. On cutting into the little 
knobs, masses of the fibres of a fungus are observed, which at 
last make their way to the surface, and there either fructify 
or become shrivelled into a whitish layer. Sometimes the 
fibres of this fungus, which are very delicate and trans- 
parent, are found throughout the whole mass of the diseased 
tuber. On examining these fibres, they present two distinct 
forms, the one being probably a variety of the other. 
I am not aware that this form of disease has prevailed very 
extensively in this country. With regard to the cause of the 
disease nothing certain is known. In Germany it has oc- 
curred in all soils and in all weathers. It has occurred to 
almost all sorts of potatoes, and after all modes of planting 
and gathering; so that many have been inclined to attribute 
it to the influence of contagion; whilst those who are advo- 
cates of the doctrine that all discases arise from the sporules 
of fungi, will at once conclude that the influence of the fungus 
in this disease is a proof that it originated in their presence. 
For the prevention of this rot every precaution should be 
taken in planting them to secure their healthful growth. The 
conclusions of Von Mariius are as follows: The newer the 
variety is, the better. The potatoes intended for seed should 
be grown separate from the rest. The seed potatoes should 
not be kept heaped up in damp cellars, and allowed to shoot 
before they are planted, and they should never be cut for 
sowing before they are brought into the field. 
