36 MANUAL OF GENERAL AGRICULTURE. 



34. NITROGEN IN PLANTS. 



Materials: Hard glass test tube, one-hole stopper to 

 fit test tube, glass and rubber tubing for delivery tube, 

 litmus paper, test tube, soda-lime.* 



Mix a gram of the dried plant material from Exercise 

 31 with ten grams soda-lime. Place the mixture in a 

 hard glass test tube about an inch in diameter. Close the 

 tube with the one hole stopper connected with a delivery 

 tube that dips into a test tube of distilled water in which 

 is placed a few small pieces of red litmus paper. Apply 

 strong heat to the hard glass test tube for four or five 

 minutes or more. Ammonia is formed from the plant 

 nitrogen and this passing over dissolves in the water. If 

 the litmus paper turns blue it is a proof that the plant 

 contained nitrogen. 



35. PLANT NUTRITION. 



Materials : Ten glass tumblers, wrapping paper, par- 

 affin, large pan, easily bent wire, six vessels that will hold 

 over 500 c.c. each, 100 Canadian field peas germinated in 

 moist sawdust, six quarts of distilled water, 2 grams of 

 calcium nitrate, 1 gram potassium nitrate, .5 gram mag- 

 nesium sulphate, .5 gram potassium acid phosphate, 1 

 gram sodium acid phosphate, .5 gram sodium nitrate, .5 

 gram sodium chlorid, .1 gram sodium sulphate, .1 gram 

 magnesium chlorid. 



For demonstrating the necessary elements for plant 

 growth, water cultures are employed. A water culture 

 containing the elements, nitrogen, phosphorous, potas- 

 sium, calcium, magnesium, sulphur and iron, in the form 

 of soluble compounds (salts) dissolved in distilled water 

 will afford more or less perfect growth. This kind of 

 water culture is known as a full nutrient solution. These 

 seven elements, in addition to hydrogen and oxygen found 

 in water, and carbon, supplied by the carbon dioxid of the 

 air, are those necessary for green plants generally. 



*Soda-lime is a mixture of caustic soda and quick lime, 

 obtainable in tight bottles; it forms an eager absorbent of carbon 

 dioxid. 



