136 



TIMliKR PINES OK THE SOUTHF.RX TNITED STATES. 



distiii};ni.sh tlio real cliarjiclcr of tlic tissues, as described later on. A more serious didicnlty 

 aiises in very old, slowly j^rowing trees, where tlie ring sometimes is representcfi by only one to 

 three cells (see fig. 18) aud occasionally disappears, i. e., is entirely wanting in some parts of the 

 cross section. Clenerally these cases, due to various causes, are too ran^ to seiiously interfere in 

 the establishment of the age of a tree. 



SPRING AND SUMMER WOOD. 



The diflerence between si)ring and summer wood is strongly marked in these pines, the 

 transition from the former to the latter being normally abrupt and giving to the annual ring the 

 a)Pi)earanc,e of two sharply delined liands. (See figs. 1.'? and 18 B.) In wide rings the transition is 

 sometimes gradual. The sjiringwood is light colored, has a specific gravity of about 0.10, and thus 

 weighs somewhat less tlian half as much as the darker summerwood, with a sjjecific gravity of 

 about 0.!»0 to 1.05, so that the weight and with it the strength of the wood is greater, the larger 

 the amount of summerwood. (See diagram, fig. 14. ) 



t-LAST S0-4-J!!!' 50 RiNGS.-i- 31° 50 RINGS.' 



'RINGS OR 50 



[yrs growth' I 



iSUMMER WOOD.' SUMMCR WOOD. I 

 -J?X- \ iO%. I 



;j, 4TH 50 RiNc^, |-CENTRAL 28 RlNGsJ 



SUMMER WOOD. 

 45/;. 



SUMMCR WOOD. 

 52%. 



SUMMCR WOOD. 

 16%. 



Flu. 13. — \'ariation of summerwood pur cuut from pith to bark. 



The absolute width of the summerwood varies generally with the width of the ring (see 

 diagram, fig. 15), i. e., the wider the ring the wider the summerwood l)aiid. It decreases in across 

 se(;tion of an old log from near the i)ith to the periphery, and in tlic same layer, from the stump 

 to the to)) of the tree. Where the giowth of the stem is ^•ery eccentric, the wood along the greater 

 radius has the greatest proportion of summerwood ; thus, in a disk of Longleaf, for instance, there 

 is on the north side a radius of 152 mm. with 27 per cent summerwood; on the south side a radius 

 of 98 mm. and a summerwood per cent of only 20 per cent. In the stuni)) section the great 

 irregularity in the contour of tiie rings is aecomi)aiiicd by a corresponding irregularity in the 

 outline of the summerwood. 



The summerwood generally forms less than half of the total volume of the whole log (see flg. 

 13); it forms a greater i)art of the coarse grained wood which was grown while the tree was 3'oung 

 than in the fine-ringed outer parts of the log, grown in the old age])eriod. It also forms a greater 

 part in the volume of the butt than of the top log, and thus fully explains the well known difference 

 in the weight, strength, and value of the various i)arts of the tree. The following table serves to 

 illustrate this point. The nuiidjcrs in each line refer to the average values for the same ten annual 

 layers through three sections of the tree at varying height. The figures in itfilics below refer to 

 si)ecific gravity for the same hiyer. The values for specific gravity were calculated on the basis of 



