32 



BOTANY. 



draws some of the water from the cell-sap, the cells thus losing their turgid, 

 ity and the tissues becoming limp or flaccid from the loss of water. 



64. The beet slice becomes rigid again in water. — Now remove some of 

 the slices of the beet from the salt solutions, wash them with water and then 

 immerse them in fresh water. In the course of thirty minutes to one hour, 

 if we examine them again, they will be found to have regained, partly or 

 completely, their rigidity. Here again we infer from the former experiment 

 with spirogyra that the substances in the cell-sap now draw water inward ; 

 that is, the diffusion current is inward through the cell walls and the proto- 

 plasmic membrane, and the tissue becomes turgid again. 



Exercise 1 5. 



65. Turgor is lost when the protoplasm is dead. — Place some slices of a red 

 beet in alcohol ; also some in hot water near the boiling point. Do the alcohol 

 and the the hot water become colored ? Why ? Determine the condition of the 



Fig- 16. Fig. 17. Fig. 18. 



Rigid condition of fresh beet Limp condition after lying in Rigid again after lying 

 section. salt solution, in water. 



Figs. 16-18. — Turgor and osmosis in slices of beet. 



slices by pressure between the fingers. Are they rigid or flaccid? Why? 

 Place them now in fresh cold water. After a quarter of an hour or longer does 

 any change take place as regards their resistance to pressure between the 

 fingers ? What is the reason for their remaining in this condition? In what 

 condition must protoplasm be in order to perform the work of a diffusion 

 membrane ? 



Exercise 1 6. 

 66. Osmose experiments with leaves. — Take leaves of various plants, like 

 the geranium, coleus, or seedlings of the squash, pea, or bean, etc. 



