The Living Trunk and Branches 137 



the one next above it, and these partitions are 

 sometimes level and sometimes set slantwise. The 

 crude sap, seeping slowly through the partitions, 

 moves through these vessels from the root-hairs 

 to the leaves. 



At home or in the schoolroom we can try a 

 simple little experiment showing how crude sap 

 travels upward through a living stem. 



" Color a glass of water with a good quality of 

 red ink," says an expert in the United States 

 Forest Service. " Place some cuttings from live 

 branches of maple or willow in this water over 

 night. The next day split one of the branches, 

 and notice how the colored fluid has been drawn 

 into and up these stems." We will then see how 

 it has traveled upward, through the youngest 

 wood. 



After the crude sap has been into the leaf 

 laboratories, and has been there made over into 

 elaborated sap, it moves slowly downward again 

 through the leaf-stalks and the boughs to some 

 actively growing point, or to some place where 

 the tree is putting away food for future use. But 

 on this return trip it travels always through the 

 inner bark, or bast. 



The elaborated sap, coming down out of the 

 leaves, travels through the inner bark by means 

 of slender tubes, " bast tubes," having their walls 

 marked with exceedingly delicate lines and pat- 

 terns. 



