LEAVES 229 



form starch; while oxygen is given back to the air. The 

 starch is then changed to grape sugar or glucose which com- 

 bines with some of the elements brought from the ground, 

 and forms proteids. Starch can only be produced in sunshine, 

 although the formation of proteids may be performed in the 

 dark. 



Another function of the leaf, which is most important, is 

 the very large evaporation of water from its surfaces. This 

 aids capillarity and osmosis, in the rise of the sap, just as the 

 burning of a lamp aids the upward motion of the oil, by remov- 

 ing the oil which is at the top. Evaporation from a leaf is 

 called transpiration. 



References : 



1. 1407 : 88-122. Leaves, Structure and Functions. 



2. 1503 : 122-141. Leaves and their Functions. 

 a. 1401:130-149. Leaves. 



6. 1402 : 90-100. Leaves and Foliage. 



c. 1403 : 24-48. Leaves. 



d. 1404:163-224. Work of Leaves. 



e. 1405:97-104. Leaves. 



/. 1406 : 15-33. The Leaf its Uses. 



g. 1505 : 92-105. Leaves Function or Work.] 



h. 1602 : 30-32. Leaves, Buds, Seeds. 



i. 1604 : 157-176. Leaves and their Work. 



./. 1609:306-314. Leaves. 



k. 1611 : 72-80. How the Leaf Gets Food from the Air. 



Experiment 78. Transpiration. 



Apparatus: Ring stand with clamp, beaker 100 c.c., glass 

 tube \" diameter, 8" long, beaker 200 c.c., tumbler. 



Materials: Mercury, wax (beeswax 90 per cent, Venice 

 turpentine 10 per cent), soil, olive oil. 



a. Cut a small branch from a vigorously growing plant and 

 seal it in one end of the tube with wax. Be careful not to 



