54 HATCH EXPERIMENT STATION. [Jan. 



affected, but those in a limited area at the bottom of the 

 slope — the wettest part of the field — began to wilt (see 

 plate). Many had already died here from the effects of the 

 first disease. It is a well-known fact that plants often wilt 

 when exposed to strong sunlight after a continued cloudy 

 and w^et period, this being due to excessive evaporation 

 or transpiration of water from the leaves. In this case, 

 however, the wilting was too pronounced to be attributed 

 to this simple physiological phenomenon. Investigation 

 showed that the leaves were not " blighted" nor w^ere they 

 affected in any way except the simple wilting, which was 

 evidently caused by some trouble at the root. Plants were 

 then dug in various portions of the affected area, and in all 

 stages of collapse, and their roots examined for the cause of 

 the trouble. It was found that there was no one ora^anism 

 (except possibly bacteria) attacking the plant, but there 

 was a general rotting, resulting from the wet condition of 

 the soil and consequent low vitality of the plant. The 

 features of this rotting varied greatly in different plants, 

 however, and scarcely any two were affected in an exactly 

 similar manner, it being almost impossible to specify a 

 feature of the disease common to all, except the wilting of 

 the tops. In the very wettest part of the affected area 

 the tubers were rotting badly. These rotten tubers were 

 swarming with l)acteria, but they were of various kinds, 

 and to no one could be ascribed the becfinnins^ of the 

 trouble. Various species of fungi were found in some, but 

 these were moulds and similar forms, and included nothing 

 which by any probability could have caused the rotting. 

 Since fungi were entirely absent in many of the rotten 

 tubers, it is certain that they did not cause the trouble. In 

 many cases the decay seemed to have started where a grub 

 of some kind had eaten into the potato. On somewhat 

 dryer ground, where the plants wilted, the tubers were not 

 rotten. In many cases, however, the stem was found to be 

 decayed just where it joins the root. The young rootlets 

 were also rotting, so that the cortex fell aw^ay from the 

 central portion. These symptoms also occurred, and more 

 pronouncedly, in cases where the tubers were rotten. In 



