AMERICAN FOREST TREES 7 



summer may do it. Perhaps not one tree in a thousand has that 

 experience in the course of its whole life. Trees in the tropics where 

 seasons are nearly the same the year through, seldom have rings. 

 Imitations of mahogany are sometimes detected by noting clearly 

 marked annual rings. It is difficult for the woodfinisher to obliterate 

 the annual rings, but some of the French woodworkers very nearly 

 accomplish it. 



No law of growth governs the width of yearly rings, but circum- 

 stances have much to do with it. When the tree's increase in size is 

 rapid, rings are broad. An uncrowded tree in good soil and climate 

 grows much faster than if circumstances are adverse. Carolina poplar 

 and black willow sometimes have rings nearly three-fourths of an inch 

 broad, while in the white bark pine, which grows above the snow line 

 in California, the rings may be so narrow as to be invisible to the naked 

 eye. 



There is no average width of yearly rings and no average age of 

 trees. A few (very few) of the sequoias, or "big trees" of California, are 

 two thousand years old. An age of six or seven centuries appears to be 

 about the limit of the oldest of the other species in this country, though 

 an authentic statement to that effect cannot be made. There are species 

 whose life average scarcely exceeds that of men. The aspen generally 

 falls before it is eighty; and fire cherry scarcely averages half of that. 

 Of all the trees cut for lumber, perhaps not one in a hundred has passed 

 the three century mark. That ratio would not hold if applied to the 

 Pacific coast alone. 



Spring and Summerwood These are not usual terms with 

 lumbermen and woodworkers, but belong more to the engineer who 

 thinks of physical properties of timber, particularly its strength. Yet, 

 sawmill and factory men are well acquainted with the two kinds of wood, 

 but they are likely to apply the term "grain" to the combination of the 

 two. 



Spring and summerwood make the annual ring. Springwood 

 grows early in the season, summerwood later. In fact, it usually is the 

 contrast in color where the summerwood of one season abuts against the 

 springwood of the next which makes the ring visible. The inside of the 

 ring that portion nearest the heart of the tree is the springwood, the 

 rest of the ring is the summerwood. The former is generally lighter in 

 color. Sometimes, and with certain species, the springwood is much 

 broader than the other. The summerwood may be a very narrow 

 band, not much wider than a fine pencil mark, but its deeper color makes 

 it quite distinct in most instances. In other instances, as with some of 

 the oaks, the summerwood is the wider part of the annual ring. The 



