MOVEMENTS OF WATER IN THE PLANT. 2/ 



tation. The turgor of a wilted plant may be restored either 

 by watering the soil or checking transpiration. 



EXPERIMENT 31. 



RESTORATION OF A WILTED PLANT BY CHECKING TRANSPIRATION. 



A plant if not too badly wilted will revive if placed under a bell- 

 jar or if transpiration is checked by other means. 



21. Guttation. If the amount of water absorbed by the 

 roots is in excess of that transpired by the leaves, it will exude 

 through rifts in the epidermis, or the water-pores, in the form of 

 drops. This process is termed guttation. It may be observed 

 in plants at the end of a warm day. The air cools quickly, 

 and its relative humidity is increased while the roots absorb 

 the same amount of water from the soil, which retains its 

 warmth for a longer time. 



EXPERIMENT 32. 



GUTTATION PRODUCED BY CHECKED TRANSPIRATION. 



Cover a plant such as Corn, Wheat, or Pea with a bell-jar and 

 place in sunlight. Note the drops of water on the leaves after an 

 hour or two. 



22. Attraction of Soil for Water. Plants cannot either by 

 the force of diffusion or of transpiration absorb all of the 

 water in the soil. Absorption finally reaches a limit beyond 

 which the capillary attraction of the soil-particles for water is 

 stronger than the combined force of diffusion and evaporation 



in the plant. 



EXPERIMENT 33. 



AMOUNT OF WATER IN THE SOIL WHICH CANNOT BE ABSORBED. 



Grow a plant (Bean) in a pot filled with rich garden soil. As 

 soon as the primordial leaves have developed, place in a room ex- 

 posed to direct sunlight, and allow it to remain without watering until 

 it wilts. Now take a sample of a few grams of the soil which has 

 been penetrated by the roots, and dry at 100 C. for an hour. Weigh. 

 It is demonstrated that the soil contained a large percentage of 

 water which the plant could not obtain to replace its evaporation. 



