Nature and Cause of the Potato Disease. 
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die. The difference observable between the two plants, so far as 
the roots are concerned, is, that the turnip can only collect the 
moisture immediately in contact with the bulbs, while the potato 
can collect it from a circle some two feet in diameter if necessary. 
And this difference extends beyond the mere space each com- 
mands, for it also extends to the manner in which the respective 
areas are covered by the roots and absorbents of the plants as 
well. In the potato, the ground is covered like a net-work by the 
main and lateral fibres and their numerous absorbents ; while in 
the turnip the whole amount of roots seldom exceeds some few 
inches of straight fibres, and the absorbents some 58 or 60 in 
number. A turnip contains more water than a potato, the aver- 
age of the turnip being about 90 per cent., while that of the potato 
in healthy seasons is full 20 per cent. less. The cuticle of the 
turnip is also about 70 or 80 times the thickness of the potato; 
so that the plants and their products are widely different from 
each other. Place the potato with its thousand of spongioles in 
the midst of moisture, and a turnip with its some 58 or 60, and the 
latter will flourish, while the former will overload itself and die 
of repletion. This may be proved by placing the two in a situa- 
tion where the roots are constantly surrounded by moisture, and 
it will be seen that although the potato apparently flourishes for 
a time, yet it becomes so surcharged with water that it ceases to 
elaborate and dies. And this must necessarily be so ; for if the 
roots absorb more water than the leaves need for the elaboration 
of the products, the prepared sap becomes weakened and vitiated, 
and soon ceases to have those properties which constitute its 
vitality ; and thus the whole functions of the plant become de- 
ranged, and if the cause which produced this derangement con- 
tinue, the circulation of the plant ceases, and it dies. The various 
parts of a plant are relatively proportioned to each other, accord- 
ing to the nature and character of the plant itself and the pro- 
ducts it is destined to form. The extent of roots and number of 
spongioles are, therefore, in strict relation to the surface and 
power of the leaves, and it is the office of the former to supply 
water and earthy salts, to enable the latter to decompose the 
carbonic acid absorbed by them from the atmosphere for the for- 
mation of its products. Now, if the spongiole absorb too much 
moisture by any adventitious circumstance, and the leaves cannot 
exhale the surplus, the water fills the cell and weakens the 
powers of the plant, and thus prevents the absorption of carbonic 
acid and the consequent assimilation of carbon. If, on the other 
hand, too little water be absorbed, or none at all, the secretions 
of the plant are more slowly performed in the first instance, and 
totally stopped in the second. The power of the roots then being 
in the ratio of that of the leaves, every class of vegetables de- 
