Plants as Affected by Excessive Water. 133 



Section III. The Plant as Affected by Unfavor- 

 able W^VTEE Supply 



A — By Excessive Water 



218. Excessive Water in the Soil Destroys the Roots of 



plants. ^Ye saw that oxygen is necessary to the life of 

 roots (90). "When the soil cavities are filled with water, 

 the roots are soon deprived of oxygen, because the little 

 oxygen contained in the water is soon exhansted (94). 

 Smothering and decay of the roots follow. Seeds planted 

 under such conditions usually fail. The soil water that 

 is most useful to land plants is that which remains at- 

 tached to the earthy particles after i^ercolation has nearly 

 ceased (capillary water). Such water is well aerated 

 because it is interspersed with cavities that are filled 

 with air. 



In the open ground, the remedy for excessive soil 

 water may usually be found in underground drainage. 

 But the same trouble often occurs in potted plants, as 

 the result of too compact soil or too copious watering. 

 The expert recognizes this condition by a sour odor of 

 the soil, by lifting the pot, or by tapping the- pot with 

 his knuckle. If the soil is soggy, the weight will betray 

 the fact, or the sound given out by the pot will be that 

 of a compact mass instead of a more or less hollow body, 

 as is the case with a pot of well-aerated soil. To remedy 

 the csil, repot the plant in fresh soil of a proper condi- 

 tion of moisture, providing abundant drainage at the 

 bottom of the pot (412). 



219. Injudicious Watering is perhaps the most common 

 cause of failure in growing potted plants. The amateur 



