STEMS 



129 



From this experiment can you discover any difference be- 

 tween monocotyl and dicotyl stems in location of sap-con- 

 ducting tissue ? 



Conclusion. State in a single sentence where sap rises 

 in each of the stems used. 



Suggestion. Make same experiment, using a potato 

 from which the lower end has been removed. Draw, indi- 

 cating with colored pencil the region of sap circulation. 



114. SAP CIRCULATION 



Object. To show that sap also circulates downward in 

 stems. 



Apparatus. Twigs of willow or poplar, knife, and wide-mouth 

 bottle. 



Method. Place the twigs in water, having cut them 

 off smooth to prevent decay. After 

 the adventitious roots have appeared 

 and become at least one inch in 

 length, carefully girdle the twig 

 about two inches above the surface 

 of the water, removing a strip of 

 bark about one inch wide. Keep the 

 apparatus standing for about two 

 weeks and cover it with a bell jar or 

 coat the twig with vaseline to prevent 

 drying out. 



What happens ? Where ? Why does 

 this prove that sap in the stem cir- 

 culates downward ? What becomes of FIG. 53. Downward cir- 

 the first crop of roots ? Why ? culation of sap ' 



Conclusion. State what evidence is here furnished that 

 sap circulates downward in a stem. 



EXP. EOT. 8 



