EFFECT OF POISONS ’ 97 
taking in or using of oxygen in respiration. Many 
parasitic plants, e.g. bacteria and fungi secrete poisons 
or induce activities in the cells of the host that lead to the 
accumulation of poisons that may destroy the life of a 
cell or lead it to abnormal growth or functioning. 
Laboratory Studies. (a) Take a piece of the root of a living 
red beet. Cutout a cube a centimeter orsoindiameter. Wash 
off the colored cell sap that has escaped from the cut cells and 
place the cube in a test tube of water. So long asthe cells are 
alive their plasma membranes prevent the colored solute in the 
cell sap from escaping. Gently heat the test tube. When the 
death point of the beet tissues is reached (below 60° C.) the 
plasma membranes are no longer impermeable and the color 
diffuses out into the surrounding water. This experiment also 
shows that the cell walls themselves are but slight obstacles 
to diffusion. Instead of by heating, similar results may be 
obtained by using certain poisons such as strong alcohol, etc., 
but care must be taken not to choose a substance that will 
destroy the coloring matter. 
(6) Set up a series of water cultures as follows: Take glass 
jars (Mason jars will do) and to keep the contents dark encase 
each with a cylinder of pasteboard which can be removed to 
permit of observation. Fill these jars nearly full of the solution 
to be tested, leaving a small air space between the water and 
the cork. The cork should have at the center a hole 5 or 
6 mm. in diameter. Germinate some peas, corn, buckwheat or 
mustard seeds. When the radicles are2 to 3 cm. long, fasten 
one seed to each cork in such a way that the root just enters the 
solution and the plumule is in a position to pass up through the 
hole in the cork (or the seed can be fastened outside with the 
root passing through the hole). Instead of a cork the jars may 
be nearly filled with water and melted paraffin poured upon it; 
after the paraffin has hardened several holes may be made 
through it by means of a hot metal rod. The water can now 
be poured out and the desired liquid poured in, nearly up to the 
under side of the paraffin. The germinated seeds can be set 
upon this paraffin cap in such a way that the radicles will pass 
through the holes. Expose all the jars to the same light and 
temperature so that as far as possible the only differences will 
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