ABSORPTION OF WATER BY PLANTS 31 



stances in solution. The cell-sap of the root-hairs, 

 and the soil water, are solutions of different densi- 

 ties, and separated by layers of porous (semiper- 

 meable) plant substance. Name these layers. 

 Experiment 10. To see what results when two liquids 

 of unequal density are separated by a porous mem- 

 brane: 



2. With a pen knife or a pair of scissors, remove a 

 portion of the shell from the large end of a hen's 

 egg, taking great care not to puncture the mem- 

 brane that separates the white of the egg from the 

 shell. 



3. Carefully place the egg thus prepared upright in 

 a glass tumbler, or beaker, and pour in tap-water 

 until the water surface is about i in. above the 



egg- 



4. By the above arrangement the solution of various 

 salts intermingled with the substance of the egg 

 serves as the more dense liquid, the water outside 

 as the less dense, while the membrane in the egg 

 acts as the porous membrane, separating the two 

 liquids. In other words, we have roughly imitated 

 the plant cell, though there is nothing in the cell 

 that corresponds to the shell of the egg. 



5. Make a careful drawing, showing the experiment 

 in longitudinal section, and about one-half natural 

 size. Label all parts. 



6. Make an observation at the end of an hour; of 

 two hours. Describe what results, and illustrate 

 the final result by another sectional drawing 

 opposite the first one. 



7. State as clearly as you can what has taken place 

 in order to produce the result observed. The 

 process is termed osmosis (Greek, osmos, pushing). 



