228 INTRODUCTION TO GENERAL SCIENCE 



References : 



1. 1407:40-69. Stems. 



2. 1407:71-79. Work of the Stem. 



3. 1503 : 98-121. Buds and Stems. 



4. Farmers' Bulletin No. 173:8, 11-14, Wood and its Structure. 



5. Farmers' Bulletin No. 181. Pruning. 



a. 1401 : 83-103. Structure of the Stem. 



b. 1402 : 14-18. Stem. 



c. 1404 : 224-285. The Work of the Stems. 



d. 1405:49-63. Stems. 



e. 1406 : 142-148. Stem Forms and Uses. 

 /. 1505:49-72. The Stem. 



g. 1606:120-122. The Processes of Growth. 



h. 1609 : 282-283. The Stem. 



i. 1611 : 86-90. Stems and then- Use. 



Experiment 77. The Pressure of Sap. 

 Apparatus: Tube J" diameter, 6' long, rubber tubing 

 \" diameter, 4' long, ring stand with clamp. 

 Materials: Growing plant in flower pot. 



a. Cut off the plant a few inches from the ground, and slip 

 the rubber tubing over the stump. Then insert the glass 

 tube in the rubber tubing and clamp to a ring stand. Fill the 

 tube with water to the height of three feet, and mark the water 

 level with a rubber band. Does the water rise in the tube ? 

 Where does the extra water come from? 



b. Nearly fill the tube with water. Does the column still 

 rise ? What causes the pressure ? 



165. LEAVES 



Leaves manufacture plant food from the raw materials, 

 which have been gathered by the roots, and transported by 

 the stems. Under the action of the sun's energy, water from 

 the root, and carbon dioxide from the air, are combined to 



