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 diseases 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 Martius 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. 



