218 Plant Physiology 



nators or pots, placing the vessels in complete darkness. Aftet 

 a few days note the color of the cotyledons and leaves, then place 

 the seedlings in strong diffuse light protected by a bell glass. 

 Observe the greening and note the time required to develop a 

 noticeable green appearance. If convenient, some of the seed- 

 lings may be put in a cold room and some at a much higher tem- 

 perature, conditions of lighting being the same ; or in the same 

 room the vessels may be circulated in one case with warm, and 

 in the other case with cold, water. Note the effect of tempera- 

 ture upon the rapidity of greening. 



Extraction of chlorophyll. Make an alcoholic solution of 

 chlorophyll from young leaves of Vicia /aba, grass, small cereal, 

 or radish. Put the leaves into a flask containing 95 per cent 

 alcohol and heat the flask carefully over a water-bath, the latter 

 being regulated to about the boiling point of alcohol (ethyl 

 alcohol, 95 per cent, boils at about 78 C.). When a fairly strong 

 extract is obtained, pour off the solution into one or more large 

 tubes and protect from the light until used ; but fresh solutions 

 should be prepared for each period. Make a careful examina- 

 tion of the solution (1) by reflected light and (2) in diffused or 

 transmitted light. In the examination by reflected light con- 

 centrate the rays upon the surface of the solution by means of 

 a hand lens. 



Decomposition of chlorophyll in alcoholic solution. Prepare 

 four small test-tubes (1 inch in diameter) each with about 15 cc. 

 of chlorophyll solution recently boiled and cooled. Place one 

 under each of the following conditions: (1) in direct sunlight; 

 (2) similar to the preceding, but with the solution covered by a 

 thin layer of olive oil ; (3) in complete darkness ; (4) similar 

 to (2) except in complete darkness. After an hour or two note 

 any change in color ; compare the tubes by holding them above 

 white paper, returning each to the same condition as before, and 

 observe after a lapse of about 24 hours. 



Separation of the chief pigments of chlorophyll. Into a test- 

 tube containing about 20 cc. of the fresh chlorophyll solution 

 reduced in alcoholic content to about 80 per cent add also 20 cc. 

 benzole. Note the position taken by the benzole, then shake 



