118 APPLICATION OF PEINCIPLES. 



Lion. If this condition is prolonged, the vegetable 

 tissue enters into a state of decomposition, and death 

 ensues. In some cases the joints of the stem sepa- 

 rate, in others the plant rots off at the ground, and 

 all such results are increased in proportion to the 

 weakness of light, and the lowness of temperature. 

 De Candolle considers that the collection of stagnant 

 water about the neck of plants prevents the free 

 access of the oxygen of the air to the roots ; but 

 it seems to me that much more mischief is produced 

 by the coldness of the soil in which water is allowed 

 to accumulate. It seems also probable that the extri- 

 cation of carburetted hydrogen gas is one cause 

 of the injury sustained by plants whose roots are sur- 

 rounded by stagnant water ; but upon this point we 

 want much more satisfactory evidence than we yet 

 possess. 



It is because of the danger of allowing any accu- 

 mulation of water about the roots of plants that 

 drainage is so very important. In very bibulous 

 soils this contrivance is unnecessary ; but in all 

 those which are tenacious, or which, from their low 

 situation, do not permit superfluous water to filter 

 away freely, such a precaution is indispensable. No 

 person has ever seen good fruit produced by trees 

 growing in lands imperfectly drained ; and all expe- 

 rienced gardeners must be acquainted with cases 

 where wet unproductive borders have been rendered 

 fruitful by contrivances which are only valuable 

 because of their efficiency in regulating the humidity 

 of the soil. Mr. Hiver {Grard. Mag., v. 60,) speaks of 



