128 SOUTH AFRICAN BOTANY 
Method.—See that the tubes are clean and dry and 
then stand them all in a beaker of water which has been 
coloured with red ink. 
Observation.—The liquid rises in the tubes, and as- 
cends highest up the tube with finest bore. 
Deduction.-—Liquids will ascend fine tubes, and if the 
tube is very fine (called a capillary tube) the liquid will 
ascend some inches. 
Vessels in the root and stem have far smaller diameters 
than any tube that can be made, hence liquids will as 
cend fairly high in roots and stems by the force of capil- 
larity alone; but this force would not be sufficient to 
cause the rise of water in tall trees, etc. this rise is due 
partly to capillarity, partly to root-pressure, and partly 
to other causes. 
Absorption of Food Materials—As has been seen, 
the water in the soil is not pure, but contains various 
dissolved substances. Roots are unable to take in their 
food in a solid form, it must be in solution. 
93. Experiment 5.—To show that roots cannot ab- 
sorb insoluble substances. 
Apparatus.—-Carmine, eosin, water, seedlings, two 
bottles. 
Method.—Fill the two bottles with water, in one put 
some eosin, in the other some carmine. Both these will 
colour the water, but the former is dissolved in it, the 
latter is not, it is only held in suspension. Place a seed- 
ling in each bottle with the roots in the coloured water. 
Result.—-In a few hours the stem and leaves of the 
seedling in eosin solution are coloured red, the other is 
unchanged. 
