TREES, SHRUBS, AND FORESTS 



391 



flowers are perfect, while others are imperfect. The trees are 

 therefore either dioecious, with male flowers on one tree and 

 female flowers on another, or polygamo-moncscious, that is, with 

 some imperfect flowers of both sexes on the same tree. 



The individual flowers (Fig. 242) have a five-lobed perianth 

 inclosing both sets of essential organs in the perfect flowers or 

 one set in the imperfect flowers. The pistillate flowers usually 



FIG. 243. A grove of sugar maples which have been tapped for 

 over eighty years 



From Bergen and CaldwelPs " Introduction to Botany " 



contain rudimentary stamens. Pollination is entomophilous, and 

 the fruits are of the samara type, the wings being formed by an 

 outgrowth from the ovary wall. 



Distribution and importance. Sugar maple is distributed over 

 the entire eastern part of the United States, occurring in the 

 northern and central hardwood forests and as a shade and orna- 

 mental tree. The wood is diffuse porous, with the ducts 

 scattered throughout the annual rings and separated by dense 

 masses of wood fibers. It is preeminently a manufacturer's wood, 

 the demand being that of a planing-mill product. These products 



