CHAPTER V. 



PHYSICAL AND MECHANICAL PROPERTIES. 



Section A. Imbibition, Hygroscopic movement, 

 Polariscope, Osmosis. 



Section B. Turgor. 



Section C. Tensions of tissues. 



Section A. 



(127) Laminaria, microscopic observation. 



The thallus of Laminaria is useful for the demonstra- 

 tion of some of the phenomena of imbibition, especially the 

 great increase in size which takes place when the dry 

 tissue is placed in water. 



Cut transverse sections of the dry stalk of Laminaria, 

 mount them in methylated spirit, and irrigate them, 

 while under the microscope, with water by placing a drop 

 of water on one side of the cover-glass and a strip of filter 

 paper on the other. Observe that the cell -walls increase 

 enormously in thickness. 



