71 



Germinate a few seeds between blotting paper, and apply blue lit- 

 mus paper. Acid property of root hairs sets free chemical compounds 

 of potash, phosphoric acid, etc., which are deposited in the soil and 

 not soluble in water. Germinate seeds in shells. 



3. Wilting of Plants. 



(a) Remove leaves from a geranium or coleus; place some in open 



aid and others under a glass. Examine in a few hours. 

 Put a branch in a jar of water with top exposed to air, and 

 one with top covered. Note any difference in twenty-four 

 hours. 



(b) What enables tender, succulent shoots to stand erect? 



(1) Remove successively strips from the petiole of a rhubarb 



leaf six inches long. Note the effect. Replace the 

 strips. What do you notice? 



(2) Cut a transverse section half an inch in length from a 



willow shoot an inch in diameter. Remove the bark. 

 Try to replace it. 



4. Root Pressure. 



Observe sap exuding from pruned branches and vines in spring. 



Root pressure in nettle sufficient to hold a column of water fifteen 

 feet; in vine, sufficient to support a column of water 6.5 feet; in birch, 

 sufficient to support a column of water 84.7 feet. 



Experiment to demonstrate root pressure. A plant in the open may 

 be used or a plant grown in a pot. Cut the stem two inches from soil. 

 Connect a long glass tube of small bore and the cut stem in the soil 

 with a short piece of rubber tubing. Moisten end of stem. 'Support 

 the glass tubing. Observe the water rising in the tube. Does it rise 

 continuously or rise and fall? 



TRANSPIRATION OF MOISTURE. 



1. Experiments. 



(a) Place a handful of fresh, green, succulent leaves with dry sur- 



faces under a glass jar and place in light or sunlight. Set 

 up another jar in exactly the same way but containing no 

 leaves. In six hours compare results. 



(b) Cover the surface of the soil of an actively growing plant, in 



a, pot, with a sheet of rubber cloth, to prevent evaporation. 

 Cover with a bell jar and place in the sunlight. 



(c) Take a young oak, maple, or peach tree. Cut a slit from the 



circumference to a small hole in the center of a circular 

 piece of cardboard. Slip the stem of the plant through slit 

 to the small hole. Seal the opening around the stem and 

 the opening to edge of cardboard. Place the cardboard over 



