Plants as Affected by Excessive Water. 137 



SECTION III. THE PLANT AS AFFECTED BY UNFAVOR- 

 ABLE WATER SUPPLY. 



A BY EXCESSIVE WATER. 



217. Excessive Water in the Soil Destroys the 

 Roots of plants. We saw that oxygen is necessary to 

 the life of roots (89). When the soil cavaties are 

 filled with water, the roots are soon deprived of oxygen, 

 because the little oxygen contained in the water is soon 

 exhausted (93). 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 attached to the earthy particles 

 after percolation has nearly ceased (capillary water). 

 Such water is well aerated because it is interspersed 

 with cavities that are filled with air (91). 



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 evil, repot the plant in fresh soil of a 

 proper condition of moisture, providing abundant 

 drainage at the bottom of the pot (412). 



seta 10 



