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. 



