CHAPTER V. 



PHYSICAL AND MECHANICAL PROPERTIES. 



Section A. Imbibition, Hygi'oscopic movement, Polar iscope, 

 Osmosis. 



Section B. Turgor. 



Section C. Tensions of tissues. 



Section A. 



(127) Laminaria^ microscojnc observation. 



The thallus of Laminaria is useful for the demonstra- 

 tion of some of the simpler phenomena of imbibition, the 

 increase in size which takes place when the dry tissue is 

 placed in water being very great. 



Cut transverse sections of the dry stalk of Laminaria, 

 mount them in alcohol, and irrigate them with water, 

 while under the microscope, 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. 



1 Laminaria has been much used for experiments on imbibition, e.g. 

 by Sachs in his Arbeiteti, ii. p. 305, and by Reinke in Hanstein's Botan. 

 Abhand. iv. 1879. 



