108 FORESTRY INVESTIGATIONS U. S. DEPARTMENT OF AGRICULTURE. 



width of the rings is normally smallest in longleaf pine, being one-twenty-fifth of an inch and less. 



(See also tables and diagrams of rate of growth in the introduction, as well as in the several 



monographs.) 



The influence of orientation on the width of the rings is completely obscured by other, more 

 potent influences, so that sometimes the radius on the north side, other times that of some other 

 side, is the greatest; and it is a common observation to see this relation vary within wide limits, 

 even in the trunk of the same tree. 



Stunted trees of longleaf pine over one hundred years old with an average width of ring 

 of one-fiftieth of an inch are frequently met with in old timber; of the other species no such 

 trees were observed. The decrease of the width of the rings from center to periphery is never 

 perfectly uniform. 'Eot only do consecutive rings differ within considerable limits, but frequently 

 zones of narrower rings, including thirty or more years' growth, disturb the general regularity. 

 Where these zones consist of very narrow rings, one-fiftieth of an inch or less, the wood is of 

 distinctly lighter color and weight. Since the value of this class of wood depends not only on its 

 strength and stiffness but also on the fineness of its rings (grain), in so far as the grain influences 

 both the appearance and the ease of shaping as well as other mechanical properties, the width of 

 the annual ring is of great importance, from a technical point of view, the finer- ringed (grained) 

 wood of the same weight always deserving and mostly receiving preference. 



The rings of the limbs are narrower than the corresponding rings of the stem. Moreover, 

 they are usually of different widths on the upper and lower side of the same branch, those of the 

 latter excelling in width those of the former. Frequently the wider lower part of a ring of a branch 

 appears like a "lune" on the cross section, quite wide (one-eighth of an inch and more) in its lower 

 median part, and scarcely visible, often entirely fading out on the upper side. This difference is 

 commonly accentuated by the appearance of the wood itself. In the upper part the wood of the 

 wing is normal and light colored, owing to a very small summerwood per cent; on the lower wide 

 part, the "lane," the wood is commonly of reddish color, either even throughout the entire width 

 of the ring, or else in several varicolored bands, which give the appearance of two or more separate 

 ill-defined rings. Sometimes the earliest formed springwood is included in this unusual coloration, 

 at other times only the median portion of the ring. This "red wood," as it has been termed by 

 the French and German writers, is composed of very thick walled cells and increases markedly 

 the weight of the wood, so that the wood of the side containing it is usually much the heaviest. 

 It is of interest that the several "lunes" in any cross section occur rarely, if ever, exactly one 

 above the other, but commonly the radius passing through the middle of one "lune" makes an 

 angle of 20 to 40 degrees with the radius passing through the middle of another "lime." Often 

 successive "lunes 77 show considerable deviation in position and commonly differ in width or degree 

 of development. Accepting the most recent explanation of this phenomenon as expressed by 

 Hartig and Cieslar, 1 it would appear that the formation of these broad "lunes" of especially 

 strong cells is due to pressure-stimulus on the growing cambium, caused by the weight of the limb 

 and its peculiar position, increased at all times by movements of the limb due to the wind. More- 

 over it seems that the formation of one well-developed "lune" relieves for a time the pressure, 

 and with it the necessity for a repetition of this formation. These "lunes" are most conspicuous 

 in the limbs of these pines near the trunk, and disappear at variable distances from the trunk and 

 with them disappears the eccentricity and the difference in appearance and weight of the wood 

 of the limbs. Immediately at the junction of limb and stem the pressure is constant, and the 

 result is the formation of almost uniformly thick-walled tissue in all parts of the ring, giving to 

 the "knot" its great weight and hardness. ( 



Lunes similar to those of the limb are frequently observed in the stems of small trees; 

 wherever this has been noted it was found on the underside of a leaning or curved portion. 2 

 Occasionally such a "lune" extends for 12 and more feet up and down. 



Quite distinct from this modification of the annual ring is another modification frequently seen, 

 especially in young trees, giving rise to so called "false" rings. It consists in the appearance of 



1 A. Cieslar. "Rotholz d. Fichte," Centralblatt f. d. g. Forstwesen 1896, p. 149, and Kobert Hartig "Das Kothholz 

 derFichte" in For&tlicJi-uaturwisseusohaftliche Zeitschrift, 1896, p. 165. 



2 Cieslar produced them at will by bending young spruce saplings. 



