FUNGOID DISEASES OF TOTAiOFS 89 



IX. Wet Rot. — This may cause serious damage 

 where potatoes are stored in a wet state. Potatoes 

 grown on wet low-lying land often suffer, and if 

 Hooded for a few days frequently become reduced 

 to a mass of pulp. 



Sympto77is. — In the "pies" individual potatoes, 

 or a mass of them, are found with the inner con- 

 tents a mass of a pulp-like consistency — hence the 

 name wet rot — and smelling strongly of butyric 

 acid. 



Cmise. — The organisms causing this disease are 

 not true fungi, two species of bacteria being largely 

 responsible, viz. Clostridiitni butyricuin and Bacillus 

 mesenteroides. These multiply in the intercellula)' 

 spaces, dissolve the cell wall, and in a very short 

 time reduce the potato to a pulp, the starch grains 

 remaining intact. The reaction of the inside at 

 the early stages is acid, but later becomes alkaline. 

 Clostridium hutyncuni flourishes only without air, 

 i.e. anaerobic. Kramer isolated an aerobic organism, 

 i.e. one which grows in the presence ot air, produc- 

 ing butyric acid and capable of causing wet rot 

 when inoculated on wounded or unwounded 

 potatoes, 



How far these organisms are assisted in thc:ir 

 attack by other fungi is not known, but certain it 

 is that they are not alone in their ravages. 



Note. — A species of Rhisocto?iia causes wet rot, and also 

 attacks the starch grains. 



