156 CONSTRUCTION OF PLANT'S FOOD 



must have been kept in the dark for forty-eight hours to ehminate 

 starch from the leaves. Before the experiment and at its close 

 test sections of leaves from both plants with chloral hydrate- 

 iodine. 



5. With a brush coat half of the under side of some leaves 

 having stomata on the under side only, with melted beeswax 

 one part and cocoa butter one part, after the leaves have been 

 covered from the light for forty-eight hours. The leaves are 

 to remain on the plant through this experiment. Scratch through 

 the upper epidermis with a needle in a few places on the upper 

 side of the coated half of some of the leaves. Now expose the 

 leaves to the light for half a day and then pick them off and 

 plunge them into cold water and peel off the wax. Extract the 

 chlorophyll from the leaves in boiling alcohol and place them in 

 a solution of iodine. Do the two halves show starch alike? 

 What do you note along the scratches ? What do these observa- 

 tions teach? Make colored drawings to show your results. 



