214 



MOVEMENTS AND EXCHANGES OF FLUIDS 



Place a few large actively growing specimens of Hclianthus in 

 sunlight at a suitable temperature, and clear away the top layers 

 of soil so that solutions poured in the pots will quickly reach the 

 roots. Instead of the usual morning supply of water given to 

 the plants pour in .3 liter of 2 per-cent. solution of lithium nitrate. 

 An hour later cut off the stem and divide the leaves and shoot 

 into a number of sections, preserving their relative positions. Now 

 beginning with the topmost section, burn it in a flame before a 

 suitable spectroscope and look for the characteristic spectrum of 

 lithium, which is characterized by a brilliant carmine red line be- 

 tween B and Cat 32. Larger quantities of the metal in the tis- 

 sue will give a carmine red tint to a colorless bunsen, or blowpipe 



flame. This may be seen best 

 through a sheet of blue glass. 

 Continue this until the presence of 

 the metal is detected. Measure the 

 distance from the section in which 

 it was found to the roots in which 

 it might have been absorbed, and 

 calculate the rate per hour. The 

 two sources of error in this test 

 consist in the time necessary for 

 the solution to be taken up by the 

 root hairs, and also in the fact 

 that the salts of lithium and other 

 substances as well are not carried 

 upward through the stem as rapidly 

 as weaker solutions or water would 

 be. 



Cut off stems of the same 

 species, and place the lower ends 



in solutions of eosin and compare the rate of conduction indicated, 

 with that determined by the lithium reaction. Negative pressure 

 should be equalized before the cut stems are placed in the colored 

 solutions. Extremely rapid conduction will be found in the 



FlG. 109. Showing path of water 

 from vessels to cells of leaf of Impa- 

 tiens pannflora. After Strasburger. 



