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XXIII. — On the Nature and Cause of the Potato Disease. By 
George Phillips. 
Prize Essay. 
Before any conclusion can be arrived at as to the nature and 
cause of the disease^ various subjects have to be considered ; and 
as these are different in character, I propose to consider them 
under separate heads, and, having done so, to conclude with the 
nature and cause of the disease itself. 
I. The Plant. — Its roots. 
The outward character of the potato plant offers nothing: 
very striking to the eye of a casual observer. Leaves, stem, and 
roots present themselves, and we see in them only the natural 
order that appears more or less in every vegetable organism. In 
this respect, indeed, all vegetables are alike, for stems, roots, 
leaves, or something analogous, appear even in the lowest class 
of plants, the fungi. These minute forms, some of whicli cannot 
be seen by the naked eye, are nevertheless as regularly organized 
as the potato : and like that too, some of them produce their own 
kind by seed as well. We cannot therefore by a glance perceive 
that the potato possesses anything uncommon in its character, 
for we see only the ordinary appendages of vegetables, and we 
see nothing beyond. And yet this plant has an arrangement of 
parts which, if closely examined, cannot fail to strike our minds 
with its fitness for certain conditions ; and we may read in those 
organs, as in a book, that which teaches us what the plant demands 
in its culture if its powers are to be healthily employed. 
Plate 3 represents a young plant growing from the set ; tlie 
stolons or strings (2) are forming ; the roots (3) are somewhat 
Plate 3. 
Young plant growing from llie set. 
1. The set. 'i. reniUilunis or slulons. 3. Roots. 
