TRANSFER. OF WATER AND MINERALS. 75 



show the presence of the color. As the dye will not enter living 

 roots, cut shoots must be used. Cut under water (see page 44) a 

 shoot of the translucent Impatiens Sultani or similar plant, and 

 transfer it, without exposure to air, to a shallow dish containing 

 water deeply stained with eosine or safranin; clamp it with its end 

 just dipping into the liquid and observe results. The exact path 

 may be determined by examining longitudinal and cross slices with 

 a lens. 

 Watching the ascent, what do you think is the power at work ? 



34. What is an average rate of ascent for water? 



Answer by observation of Experiment 16. Is the rate of 

 ascent of the dye probably the same as the natural ascent of 

 sap in the uninjured plant ? 



The usual method of testing this is by use of Lithium salts recog- 

 nized spectroscopically (see Detmer-Moor, 233). This test is said to be 

 not difficult to apply. 



35. What is the anatomical structure of the water-conducting 

 tissues of a plant? 



Answer by studies on the stems of such typical plants as 

 Aristolochia and Zea (or by review of earlier studies). Con- 

 struct a diagram of the stem as a sap-conducting- apparatus. 



In the examination of the stem carrying dyed water, you 

 find that walls as well as cavities contain the color, which sug- 

 gests the possibility of water-passage in the walls. 



36. Can cell-walls transfer water ? 

 Answer by Experiment 17. 



EXPERIMENT 17. This may be tested by supplying water to one 

 part of a mass of tissue composed of dead cell-walls only and noting 

 whether it spreads. Select a piece of dry wood a few r cm. square 

 and 3-5 mm. thick ; allow a strip of filter-paper, with one end in a 

 water-reservoir, to rest against the middle of its under side, and 

 carefully note the result, explaining it in terms of micellar processes, 

 and diagramming the principal stages in the result. 



Dees the effect upon the wood suggest a merely passive absorp- 

 tion of the water, or a more energetic process ? 



This may be answered by noting how much power is needed to force 

 a warped piece of the wood back into its former shape, though this will 

 not give a measure of the molecular force involved in the imbibition. 



