LEAVES 151 



relation to the framework? Trace one of the main veins 

 to its termination. What do you find there? Is there 

 any relation between the feather veining and the outline? 



Conclusion. State the relation of form to framework 

 of leaves. 



131. LEAVES 



Object. To find out where tl\e sap flows in a leaf. 



Apparatus. Stems bearing leaves or leaves with long leaf- 

 stalks, a bottle, and eosin solution. 



Method. Treat the leaves in the same manner as the 

 root was treated in Experiments 75 and 113. Where does 

 the leaf become stained? Cut off sections of the leafstalk 

 and see if you can tell where sap flows in that part. If this 

 experiment is made with large, coarse leaves like rhubarb, 

 burdock, celery, or cabbage, some very pretty results will 

 follow. 



Conclusion. State what part of the leaf furnishes a 

 channel for sap circulation. 



132. LEAVES 



Object. To show that leaves exert an upward pull on 

 sap flow. 



Apparatus. A vigorous young shoot of ailanthus or other 

 equally strong plant, rubber tube, glass tube, beaker, retort clamp, 

 and mercury. 



Method. Cut off the branch under water to prevent 

 entrance of air at the cut surface. 



Fit the piece of rubber tubing tightly about the stem and 

 insert the other end in the glass tube, fitting it air-tight. 

 Wax the joint as an additional precaution and fill the glass 



