The Ascent of Sap 127 



A sudden frost when the sap is moving freezes 

 all the fluid in the wood. When this happens the 

 trunk cracks open, and if the split goes deep, the 

 tree dies. Many Florida orange trees have thus 

 been killed by a return of winter after spring had 

 come, apparently to stay. If the frost crack is but 

 shallow, nature, after awhile, heals the wound, 

 but the trunk will bear always a lengthwise scar. 



When the upward streaming has fairly begun 

 the lumbering season is over, for wood cut " in 

 the sap " will soon decay. 



The mounting fluid contains some mineral sub- 

 stances taken up by the root-hairs, but it consists 

 mainly of water, mucilage, and glucose. 



In early spring some trees are so full of sap 

 that it oozes slowly from any deep cut made in the 

 bark. The maple, beech, birch, and butternut all 

 " bleed " in this way if they are wounded early 

 in the season before their leaves unfold. 



The sap of all these trees contains so much 

 sugar that it can be fermented. " When I was a 

 schoolboy," says an English writer of sixty years 

 ago, " wine used to be made every year from the 

 birch woods near my home. This wine was sweet 

 and pleasant to the taste." 



In early spring a sweet sap flows from wounds 

 made in the trunk of the canoe-birch, and this 

 supplies the Indians with a pleasant, cooling drink. 

 By boiling, it can be made into syrup. 



Sugar has been made from the Norway maple, 



