PHYSIOLOGICAL PROCESSES IN PLANTS 



97 



the leaf, and there unite to form elaborated foods, as starch, 

 sugar, proteids, and oils. 



Conclusions. 1. If leaves absorb sunlight, they may there- 

 fore absorb energy. This energy is probably absorbed by the 

 chlorophyll and is used in forming elaborated foods from soil 



FIG. 27. Diagram showing the essential working parts of a leaf. Note the 

 stoma and the two tubes, one of which brings raw materials to the leaf, the 

 other for removing the manufactured materials from the leaf. 



and air foods spoken of above. Where is most of the chloro- 

 phyll located ? Then where are most of the plant foods elab- 

 orated or built up ? 



2. Write a paragraph of description, telling all that is 

 shown in Figure 27. 



Observation. Put a small plant, as a geranium, in a 

 dark room for several days, so that the starch present in the 

 leaves may be exhausted. Remove the plant from the dark 

 room, and cover the lower surfaces of a few leaves with vas- 

 eline. Expose the plant to direct sunlight for a few hours. 

 Pick off the leaves with the vaseline, also some without it, and 

 dissolve out the chlorophyll with wood alcohol. Then place 

 SHARPE'S LAB. MAN. -7 



