40 BOTANY. 



of the protoplasm on the elastic cell wall makes the cell turgid. 

 So we found in the experiments with the slices of beet in the salt 

 solution and water that the partial removal of the water from the 

 beet leaves the slices limp, while they regain their rigidity if the 

 salt solution is removed and the slices are placed in water. We 

 should now endeavor to see if water plays any part in the rigidity 

 of plant parts, as in the case of shoots, leaves, etc., and in what 

 way this rigidity may be lost and regained. 



Exercise 2O. 



83. Loss of turgidity in cut shoots. From a living geranium, balsam, 

 coleus, or other plant, cut a leafy shoot i^cin to 2Ocm long. Leave it in a 



dry room for a short while until 

 it partly wilts. Grasp the shoot 

 at the cut end and attempt to 

 hold it erect. How does it now 

 compare with its condition when 

 first cut from the plant ? 



84. Eestoration of turgidity 

 in shoots. Take the leafy shoot 

 used in paragraph 83. (It should 

 not be so wilted that any portion 

 of it is dry.) Cut the end fresh 

 again and place it in a vessel of 



H,^ water, and if the room is dry, 



' cover the vessel and shoot with 



a tall glass cylinder or bell jar. 

 Observe the result in a few hours, 

 or on the following day. 



85. Longitudinal tissue 

 tension. For this in early 

 summer one may use the 

 young and succulent shoots 

 of the elder (sambucus); 



Same plant photoglpheffour hours later. It Or the petioles of rhubarb 



during the summer and early 

 autumn; or the petioles of richardia. Petioles of caladium are 



