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** tinuous cultivation of crops from year to year in the same areas must 
“ tend to keep up a continuous supply of the parasite, the sclerotial 
* masses of mycelium within the vessels being very well adapted to 
“ survive prolonged period of dormancy, with a capacity for renewed 
«€ 1 » 
little or no sign of disturbance, but at a point about an inch below the 
soil-surface a brown stain makes its appearance in the substance of the 
within 24 hours, is a marked and peculiar s p n à further com- 
munication Dr. Cunningham says:—* None of the specimens of the 
* blight which I have seen show any trace of spore formation, but the 
** of propagati 
“ other vegetable blights; and, if so, the delay in the appearance of the 
* disease is readily accounted for, as sclerotia frequently require a con- 
ide i roused f i 
country. So far it has been shown :— 
(i.) ‘Fhat the disease is not the European potato blight. From 
and of the characteristic odour; and it differs also in not being 
amenable, when the crop is in the ground, to treatment by the 
sulphate of iron and copper solutions. 
(ii) That diagnostic symptoms may be found, before the characteristic 
ring of tuber is apparent, in the sudden wilting of the green top, 
and in the antecedent brown discoloration of the fibro-vascular 
bundles of the haulm discoverable on section, — 
(ii) That the disease germ harbours in the soil, and will infect all 
stocks however robust. 
9. The origin of the pest is probably to be found in exhaustion of the 
soil and of the stock owing to over cultivation. The crop is so 
profitabie that it is grown year after year on the same land, and the 
unwillingness of the cultivator to exchange it for less valuable produce, 
even when disease is rife, forms one of the chief difficulties to be met. 
A rest from potato for three or four years would probably cleanse 
infected land. wd i 
