428 AMERICAN FOREST TREES 



It is one of the most vigorous and dependable of trees. It does 

 not grow fast, but it keeps steadily at it a long time, and enjoys unusually 

 good health. Its worst enemy is coal smoke, but fortunately, most 

 sugar maple forests are out of reach of that disturber, though shade 

 trees near factory towns and in the vicinity of coke ovens often suffer. 

 Woodlots of sugar maple, occupying corners of farms in the northern 

 states from Minnesota to Maine, present pictures of health, vigor, cleanli- 

 ness, and beauty which no forest tree surpasses. The intense green and 

 the density of the crowns in summer make the trees conspicuous in any 

 landscape where they occur, while their brilliant colors in autumn are 

 the chief glory of the forest where they abound. 



The wood of this tree is hard, strong, and dense. It is three 

 pounds lighter per cubic foot than white oak, and theoretically it rates a 

 little lower in fuel value, but those who use both woods as fuel consider 

 maple worth mo^e. It is thirty per cent stronger than white oak, and 

 fifty-three per cent stiffer. The wood is diffuse-porous, that is, the 

 pores are not arranged in bands or rows, as they usually are in oaks, but 

 are scattered in all parts. They are too small to be seen with the naked 

 eye, but under a magnifying glass they are visible in large numbers. 

 The yearly ring is not very distinct, because of the slight contrast 

 between spring and summerwood. The medullary rays are numerous 

 but small. In wood sawed along radial lines, from heart to sap, small 

 silvery flecks are numerous. These are the medullary rays. They add 

 something to the appearance of quarter-sawed maple, but not enough 

 to induce mills to turn out much of it. 



Such figures as maple has are brought out best in tangential sawing 

 that is, cut like a slab off the side of the log. Three distinct figures are 

 recognized in sugar maple, and to some extent they belong to other 

 maples. These forms of wood are known as birdseye, curly, and blister 

 maple. They are accidental forms and exist in certain trees only. 

 Students of wood structure are not wholly agreed as to the cause of these 

 forms, but one of them, the birdseye effect, is believed to be due to 

 adventitious buds which distort the wood in their vicinity. These buds 

 start near the center of the tree when it is small, but never succeed in 

 forcing their way out. They remain just beneath the bark during most 

 or the whole of the tree's life. A pin-like core, resembling a fine 

 thread, connects the birdseye with the tree's pith. This thread is the 

 pith of the embryonic branch formed by the bud which never breaks 

 through the bark. When the wood is sawed tangentially, small, dark- 

 brown points or dots show the center of the buds, or the pith line con- 

 necting it with the tree's center. Curly maple and blister maple are 

 not believed to be formed in the same way as birdseye. 



