17 
•'No. 3. Twenty sets that had been kept warm and moist for 
about half the time that No. 2 had, and from which the shoots, 
three inches in length, had been removed only twice. All the 
sets were planted on the same morning, each exactly six inches 
below the surface, and with an unsprouted eye upwards. The 
spring was genial. Of No. 1, nineteen plants came up. The 
twentieth seemed to have been removed by an accident. Of the 
nineteen not one was curled. The produce a full average crop. 
Of No. 2, all came up, but from ten to fourteen days later than 
those of No. 1, and three of the plants sixteen days later. Four- 
teen of the plants were curled. Of No. 3, all came up, but from 
ten to fourteen days later than those of No 1. Four plants 
were as severely curled as those in No. 2, eight were less so, 
and the remainder not at all ; but of these the produce was 
below an average, and a full fortnight later in ripening. Dick- 
son, Crichton, Knight, and others have found, tfjat tubers taken 
up before they are fully ripened, produce plants not so liable to 
the curl as those that have remained in the ground until com- 
pletely perfected ; and, I believe, under ordinary treatment, this 
to be the fact, for it is rational. The process of ripening pro- 
ceeds in the potato, as in the apple, after it has been gathered, 
and until that is perfected it is accumulating vigour, shews no 
appetency to vegetate,consequently is not exhaustingits vitality, 
which is a great point, considering the careless mode usually 
adopted to store them through the winter; for this energy com- 
mences its decline from the moment it begins to develope the 
parts of the future plant Tubers taken from the soil before 
perfectly ripe, never are so early in showing symptoms of vege- 
tation. Crichton, Hunter, and Y oung, in some of the works 
before referred to, have also agreed, that exposing the sets to 
light and air, allowing them to become dry and shrivelled, also 
induces the curl in the plants arising from them. This result 
of experience also confirms my conclusion, that the disease arises 
from deficient vital energy ; for no process more than this dry- 
ing one of exposure to the light and air, tends to take away 
from a tuber the power of vegetating altogether.” 
Evidence in favour of this theory is given from the practice 
of a farmer, who it is stated " employed rather small sets ; 
cutting a moderate-sized potato into at least two pieces. Un- 
favourable weather, other business, and a somewhat dilatory 
2^9. ACCTAJIICM. 
