EXOGENOUS SERIES-BROADLEAF WOODS. 41 



tapped, and sugar is also present in the sap of other trees, such 

 as the butternut and birch. A sugar maple will, on an 

 average, produce about twenty-five gallons of sap, containing 

 a total of about six pounds of sugar, in a season. 



The Boxelder (Acer negundo] is a true maple, remarkable 

 in that it is widely distributed from Canada to Mexico and 

 from the Atlantic to the Rocky 

 Mountains, on low bottom lands, 

 and at elevations of five thousand 

 and six thousand feet.* The trees 

 are beautiful and, like other maples 

 are valued for ornamental purposes. 

 The soft, light wood is not partic- 

 ularly noted, although occasionally 

 used for woodenware, interior finish, 

 and paper-pulp. Small quantities 

 of sugar are present in the sap of 

 this tree. 



The maples may be told by their 

 leaves of characteristic shape, but 

 chiefly by their two-seeded fruit or 

 " keys," the two wings of which 

 spread differently in different species. 

 The leaves of some species change 



Box Elder, b, Hard or Sugar 

 Maple, c, Soft or Red Maple. 

 of, Soft or Silver Maple. 



in autumn from green to red and other brilliant colors. Those 

 of other species change to yellow without trace of red. Sixty 

 to seventy species have been distinguished, nine of which occur 

 in North America. 



* Sargent. 



