ABSORPTION OF WATER AND MINERALS 05 



)% solution of potassium ferrocyanide (using care, for it is poison- 

 ous) ; drop quickly into it a compact small lump of copper chlo- 

 ride (or copper sulphate), which should sink to the bottom. Ob- 

 serve carefully the growth of the membrane, and form a clear and 

 consistent mental picture of the molecular processes and the energy 

 involved. Express these in a diagram. (This is worth observing 

 also upon a slide under the microscope.) 



22. What is the physical explanation of the results of the fol- 

 lowing simple experiments? 



EXPERIMENT 8. (a) In five test-tubes place respectively water, a 

 25^, a 50^, a 75 r /, and a ioo solution of a saturated solution of sugar. 

 Drop one or two raisins into each, and add formaline to make a 2% 

 solution to prevent fermentation. 



(I)) Fill a hollow cut in a piece of beet (or carrot) with dry sugar. 



(c) Boil a piece of red beet for a few minutes, and then place it in 

 fresh water. In another dish of water place a similar but unboiled 

 piece. Observe the effect, after a few days, upon the water. 



What is the explanation of the bursting or collapsing of 

 fruits in preserving ? Of the crispness of celery when placed 

 in water ? 



What other every-day osmotic phenomena can you think 

 of? 



It is said that the exact relationship of the killing of the protoplasm 

 to the release of the color in the experiment 8 c may be determined 

 beautifully by using thin slices of beet under the microscope, and apply- 

 ing the heat by the temperature-stage. 



23. Can an apparatus be constructed to imitate the principle of 

 the physical process of water and mineral absorption by roots ? 



Answer bv observation of the construction and working of 



* o 



the Pfeffer artificial cell. 



Though simple in principle, it is practically difficult to set 

 up for action; so, instead, read the account of it in Goodale, 

 Physiology ) 226-230, in careful comparison with t/te speci- 

 men oti the table. Place a synoptical account of it in the 

 note-book. 



Construct two diagrams showing comparative structure and dif- 

 ferences in operation of this apparatus and of the absorbing system 

 of the root; especially note the duration of absorption in the two 

 cases, and its determinants. 



