194 Some Simple Physiological Demonsiraiions. 
ends of the branches are fitted on to the free ends of the glass 
tubes with rubber tubing as before but without the column of water 
above, while their lower ends dip into beakers filled with water. 
The surface of the branches should previously be coated with a 
layer of paraffin wax so as to close up all apertures and scars. 
The relative conducting powers of the two branches will of course 
be proportional to the heights of the columns of water that form in 
the glass tubes above their cut ends. 
5. Demonstration of water-pores .—We have adopted the same 
principle for the rapid demonstration of water-pores. To the 
longer arm of the tube is attached a glass cylinder supplied at both 
ends with rubber corks perforated by a single hole and sufficiently 
wide to accommodate the leafy portion of the branch to be 
experimented with. The branch is inserted through the hole 1 in 
the lower cork so that its foliage is situated within the glass 
cylinder, whilst the lower cut end of the branch projects below the 
cork into a beaker of water. Owing to the reduced pressure 
produced in the apparatus as before, a considerable quantity of 
water is sucked up into the shoot, and drops of moisture are soon 
formed over the water-pores. Branches of Fuchsia give a good 
result. 
6. Demonstration of the shrinkage of an herbaceous plant as the 
result of loss of turgescence .—The importance of turgescence in 
maintaining the rigidity of an herbaceous plant is easily demonstrated 
by familiar methods, but a means of making the resulting shrinkage 
obvious to a whole class has not, as far as we are aware, been yet 
described. We use for this purpose a simple lever working over 
the surface of an arc, graduated to show the actual distance to 
which the movement of the long arm of the lever corresponds 
(Fig. 1, C). To the short arm of the lever (c in Fig. 1, C) an entire 
herbaceous plant is firmly tied by its apex, and to the other end of 
the plant is attached a weight sufficiently heavy (one to two pounds) 
to keep the plant in position at the base of the glass cylinder b 
(Fig. 1, C). The latter should be tall enough to include the whole 
plant. If necessary, sufficient weights can be attached to the long 
arm of the lever to keep the plant fully extended without undue 
strain. The cylinder is now carefully filled with strong salt solution 
and the position of the pointer on the graduated arc noted. After 
about half-an-hour the pointer on the arc will record a shrinkage 
of a quarter to half an inch according to the nature and size of the 
plant used in the experiment. If the salt solution is then siphoned 
off and replaced by water, the gradual recovery of the plant can be 
noted in the same way. 
1 An excellent method of fitting a branch into a rubber cork is described 
and figured by Osterhout, “ Experiments with Plants,” 1908, p. 205, Fig. 118. 
