OSMOSE. 23 



remove a little of the water from the bottom of the tumbler by 

 means of a small tube or pipette, and test it for chlorides. 



II. Osmose. Diffusiox through a Membrane. 



Scoop out a small cavity in a fleshy root, for instance that of 

 a carrot, and carefullj- dry it with a cloth. Then fill it with fine 

 sugar, and let the root stand in some place where it will not 

 be disturbed. Note any changes which take place in the sugar 

 and in the condition of the root. By comparative examinations 

 of the tissues removed and those remaining, ascertain whether 

 any of the sugar has entered the cells. 



Tie a thin, sound piece of parchment paper (or, better still, 

 parchment) over the mouth of a thistle-funnel, and fill the bulb 

 of the funnel with a strong solution of common salt. Then sus- 

 pend the funnel in pure water, so tliat the level of the water 

 outside corresponds to that of the brine inside, and keep the ap- 

 paratus in a warm place, noting an^- change of level of the liquid 

 in the funnel tube. Trj- other substances in the tube ; for in- 

 stance, dilute potassic hydrate, concentrated potassic hj-drate, 

 sj-rup, and diy powdered gum-arabic. 



Carefull}' examine the upper surface of the leaf of Lilac, Olean- 

 der, or Echeveria for the presence of stomata, and if none are 

 found, make the following trial witli a good, sound, young leaf, 

 being careful to see that the plant is well watered. Put a drop 

 of water on the upper surface of the leaf, and dust upon it 

 either finely powdered sugar or salt, until the drop has taken 

 up all it can, and the mass looks nearly- dry ; then blow off the 

 residue, and cover the leaf or plant witii a bell-jar. Keep it in 

 a warm place and water well. Observe in the course of a few 

 hours, and at frequent intervals during the next four or five da3-s, 

 any changes which the spot of sugar undergoes. It is a good 

 plan to prepare several such spots with difl['erent substances. 



III. Pelliolk PEEOirrrATES. — Tuaube's Artificial Cei.l. 



Dissolve 5 grams of pure potassic ferrocyanide in 100 cubic 

 centimeters of pure water. Place some of the solution in a test- 

 tube having a foot, and drop into the tube a small fragment of 

 moist chloride of copper. Observe the changes which take place 

 in the shape of the film which instantly forms around the frag- 

 ment. Try the same experiment with a saturated solution of 

 potassic ferrocyanide, and afterwards with solutions containing 

 respectivelj' 1 and 10 per cent of the ferrocyanide. 



