THE POTATO DISEASE. 



179 



will be easily multiplied in the same manner, as well as by 

 cuttings of the young stems, during the summer months, when 

 the plant is growing. It will grow in any common garden soil, 

 and is best adapted for situations which are sheltered from high 

 winds. 



XXVI. — Observations and Experiments made in the Garden 

 of the Society in 1846 relative to the Potato Disease. By 

 Mr. Robert Thompson, Superintendent of the Orchard and 

 Kitchen Garden. 



The continuation of the disease having been indicated in the 

 previous winter by some potatoes growing in a frame, the crops 

 in the open ground were closely watched ; and it was found that 

 even in the end of June, although the tops were then growing 

 vigorously, and had a fresh green appearance, the disease had 

 commenced in the same way as in 1845, exhibiting itself first on the 

 portion of stem below ground, where, in consequence, sufficient 

 roots had not been formed to support the top for any length of 

 time, especially under the evaporating effect of very hot weather. 

 Immediately above the surface of the ground the stem appeared 

 thicker than usual, from the returning sap having no farther any 

 sound channels to enable it to pass freely to the roots and 

 tubers. 



As an experiment to ascertain whether a set of fresh roots 

 might not possibly be formed, the stems of those in a quarter in 

 the kitchen garden in which the disease was most apparent, were 

 additionally earthed up, June 26, with the view of encouraging 

 fresh roots from the stem above where the disease had previously 

 spoiled it. This proceeding had the effect of producing some fresh 

 roots, tending to keep the tops green throughout the hot weather, 

 but insufficient to maintain them in a perfectly healthy condition, 

 or to enable them to withstand the vicissitude of a change from 

 very hot to wet weather. The tubers grew tolerably well, although 

 their quality was very different from that which the varieties 

 possessed in former years. Nor was this to be wondered at, the 

 stem whence the runners proceeded being unsound, whilst the 

 runners themselves in most cases afforded only a disorganized 

 communication. Potatoes not fully grown had the flavour of 

 very old ones ; and frequently their skins had nearly the same 

 appearance as that of the old set, with which, indeed, the entire 

 substance of the tubers seemed too much assimilated. 



In the beginning of July a stem was taken up with the tubers 

 attached. Disease was perceptible on the portion of stem below 

 ground, but the tubers were then sound. The stem and at- 

 tached tubers were replaced in the ground ; but being an early 



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