130 STEMS 



115. SAP CIRCULATION 

 Object. To demonstrate sap circulation in trees. 



Method. Bind a branch tightly by winding a wire about 

 it several times. 



What is the effect on growth above the wire ? 



What is the effect on growth below the wire ? 



Give reasons for the result in each case. 



Suggestion. Procure twigs on which bagworms have 

 hung their cocoons and make an examination of the point 

 about which the web was fastened. How does it compare 

 with the portions on both sides of it? Cut such a twig 

 through the middle and examine the section exposed. What 

 does this show regarding sap circulation in the twig? 



Examine a tree about which a wire clothesline has been 

 placed. How has its growth above and below the wire 

 been affected ? 



What effect follows the use of shade tree branches as 

 anchorages for telephone, telegraph, and electric light poles, 

 etc.? 



116. SAP PRESSURE OR ROOT PRESSURE 



Object. To measure the pressure due to the upward 

 flow of sap in a plant. 



Apparatus. A vigorous plant of hydrangea having a stem about 

 half an inch in diameter, a T-tube, a bent gauge tube, stoppers, 

 rubber connections, and mercury. 



Method. Cut off the stem of the plant about four inches 

 from the ground and quickly attach the T-tube before the 

 cut surface can become dry. Arrange the apparatus as in 

 Figure 54 and stand it in a favorable location. Water the 

 soil and await results. 



