12 



the adjacent district of Quebec the forest growth is often almost pure 

 maple, and even considerably farther south, where beech and birch 

 become associate trees, the sugar maple holds its own as the dominant 

 species. In northern Pennsylvania, at an altitude of over 1,000 feet, 

 the mixture is much the same as it is in New York. In Ohio, Indiana, 

 and Illinois a similar condition is found; but as the hilly country 

 disappears the maple retreats to the richer and damper soils, leaving 

 great areas to the oaks, chestnuts, etc. This is particularly true of 

 the southern parts of these States. By the time the western and 

 southwestern limits of its range have been reached it has only a scat- 

 tered occurrence, even in the most favorable positions. In southern 

 Michigan the forests are similar to those in New York, but as one 

 approaches the pine region of the North the maple confines itself to 

 the more fertile places. The same is true of Wisconsin and Minne- 

 sota, where the sugar maple reaches its northwestern limit in the 

 United States. 



Maple trees are often seriously injured by an insect commonly 

 called the " maple worm," concerning which information may be had 

 by application to the Bureau of Entomology, United States Depart- 

 ment of Agriculture. 



In the present discussion the sugar maple is not considered as a 

 lumber tree, for which a long stem free of branches is desired, but 

 rather as a paying producer of sap. Under this aspect a silvicultural 

 problem is presented radically different from that which ordinarily 

 confronts the forester. (See p. 14.) The full and heavy crown with 

 a large leaf surface must be developed in place of the long, clear 

 stem. The sap flow must be continuous and plentiful. The best sap 

 flow is where the transition from winter to spring is slow, where the 

 days are warm and sunny and the nights frosty. These conditions 

 do not occur throughout the entire range of the species. A locality 

 wherein the ground thaws quickly and which has no great variation 

 of temperature between day and night is not suitable for sap produc- 

 tion. The "season" must be long enough, also, to insure sap in 

 merchantable quantities. Such conditions are characteristic only in 

 the Northern States, and as sugar making goes farther south it can be 

 profitable only at altitudes which reproduce the climatic conditions of 



the North. 



THE BLACK MAPLE. 



The black maple is generally considered superior to all others as a 

 producer of sap. How far this is true is uncertain. In its general 

 silvical characteristics it is similar to the sugar maple, save in the fact 

 that it seems to prefer lower land, such as the banks of streams and 

 rich alluvial river bottoms. It is found in Vermont on the shores of 

 Lake Champlain, and ranges southward, west of the Alleghenies, 

 from Minnesota to Arkansas and eastern Kansas. 



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