100 QUARTERLY JOURNAL. 



ing first died down, and thus indicated the disease, it has suggested 

 itself to me, even if this fungus is really a subterranean species, 

 whether it has not been propagated and disseminated by spores 

 floating in the atmosphere and attaching themselves to the stalk of 

 the potatoe, on that vegetating and extending themselves down- 

 wards until they reached the point of junction with the tuber, 

 there producing decay, and the death of the upper part of the 

 vegetable, and afterwards disseminating themselves through the 

 tuber. 



A parallel to this probably exists in the mushroom^ a fungus 

 which is naturally produced from horse droppings, when by being 

 kept dry for a considerable time, they have arrived at a favorable 

 state for the development of the spores. These spores have pro- 

 bably attached themselves to the stems of hay which has been eaten 

 by the horse, have passed through its stomach and remained in an 

 inert state, until favorable circumstances have produced their de- 

 velopment in the droppings. 



I regret that I had not commenced this investigation early enough 

 to have examined the stalk and Its junction with the tuber, wdth 

 the microscope, on the first appearance of its drooping, as all the 

 proof now to be expected from experiments, can only be of a nega- 

 tive character : however, here are such results as I have obtained : 



1st. One of these much diseased potatoes was cut in halves ; 

 each half was placed on half a sound potatoe, in perfect contact, 

 placed under a bell glass in a damp, dark atmosphere, temperature 

 57° to 62°. In five days the sound potatoe was not in the slight- 

 est degree contaminated with the fungus or the worms. 



2d. A whole diseased potatoe covered with black spots, was 

 placed under a glass, in the same circumstances as experiment No. 

 1, in contact with a whole sound potatoe. The fifth day the sound 

 potatoe remained uncontaminated and without worms. 



3d. A whole and much diseased potatoe was buried two inches 

 below the soil, which was damp but not wet. A sound potatoe 

 was buried in the same soil, two and a half inches distant from it, 

 the temperature kept as before — 57° to 62°, In five days this latter 

 remained quite sound. 



It is possible that five days is not long enough ; I have therefore 

 left them all in the satne state, and shall not touch them for three 

 or four weeks. 



