RADIALS 23 



Scotch pine from Os, Norway, which had a 3-inch radius on one side 

 and a 9-inch radius on the other. The maximum radius was used and 

 it cross-identified in a perfectly satisfactory manner. Several of the 

 trees from that locality showed a very rare characteristic in having 

 the eccentricity change its direction as the tree grew older, due prob- 

 ably to change in surrounding growth. This was less easily avoided. 

 Forest Service men usually prefer a mean radius in eccentricities, but 

 in this work it is not desirable, because in that kind of a radial the 

 rings are apt to be inclined, making perpendicular measurement more 

 difficult. 



Missing rings — In eccentricity the crowding in the shorter radius 

 causes some rings to disappear altogether instead of merely becoming 

 more minute. The same failure of rings is very apt to occur between 

 lobes, especially in junipers. Hence in boring trees it is safer to choose 

 the lobe itself than the depression between lobes. 



Lobes — In the case of lobes, or the scalloped outline of a tree-trunk, 

 the variations observed in eccentricity are greatly exaggerated, in 

 fact, so much so that trees like juniper and pinyon that go strongly 

 to lobes can not well be used in ring studies. In an extreme, a given 

 ring can not be traced from lobe to lobe. Such a tree of course has 

 doubtful value. 



Pines and sequoias, however, have only a negligible lobe effect, 

 except during the "infancy" period of the sequoias, when the lobes 

 are very marked. They disappear in the early "youth" rings, which 

 are really the earliest ones of any chronological value. When not 

 pronounced, either the lobe itself or the depression between two lobes 

 may be taken as the location of a radial, for the rings remain at right 

 angles to its direction. 



Root influence — Lobes are usually more pronounced at the base 

 of the trunk and show evident connection with the roots. Since the 

 root supplies the sap which passes up the trunk and, in passing, forms 

 the ring, the rings, it would seem, depend upon the way the sap spreads 

 out around the tree as well as upon vertical movement. So in old 

 trees whose rings are naturally crowded, we find some missing here 

 and there in the circuit without much lobe effect being evident. In 

 the general use of at least five trees in a group, such lapses practically 

 always come to light. 



Gross-rings — A difficulty in the selection of radius in sequoias 

 has been occasional radii where the rings are greatly enlarged. These 

 are called "gross-rings." They are probably associated with the 

 success of some certain root and therefore formed lobes or projecting 

 curves about the trunk when the tree was growing at that size. Some- 

 times these areas extend directly to a projecting curve of the stump 

 outline and their relationship is evident. They not merely exaggerate 



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