122 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I40 



Table 49. — Incidence of single and multiple grozvth layers in annual increments 



Number of Single 



Number of Number of blocks and All 



trees branches sectioned All single multiple multiple 



CCCb I I I — — 5 



CMJ I I 2 — — 4 



Con A I I 2 — — 2 



Con P I 2 4 I — 3 



Con T 3 41 148 49 7 44 



MP I 2 7 — I 2 



SA 2 6 16 IS 3 14 



TTAp 2 7 27 — 4 ID 



TTC 10 86 225 47 54 143 



TTCw I 7 14 7 2 2 



TTJ 5 21 59 30 12 28 



TTL 5 IS 27 2S — 2 



TTM 2 12 35 9 s 7 



TTP 5 97 260 112 43 97 



TTS I I I I — 4 



TTTh I I I I — 3 



TTV I I I — — 3 



WAp I 2 7 I — 2 



WCh 2 6 14 — 6 2 



WPe I 6 19 2 2 3 



WPI I 2 s 2 — — 



XSC II 40 118 19 15 157 



XSJf 2 3 7 6 - 7 



XSP 2 5 ID 9 3 II 



YCt 4 14 26 — I 28 



Total 67 380 1036 336 158 583 



growth layers whereas others have single growth layers. Therefore, 

 the actual percentage of years with multiple growth layers is some- 

 what greater than 63. It must be remembered, of course, that some 

 of the years with singles may actually have been multiple at places on 

 the branches not represented by sections. 



Among the trees from which many sections were cut, species does 

 not seem to be the controlling factor in multiplicity. The following 

 show more than 50 percent of the years with multiple growth layers : 

 loblolly pine (Con T), shrubalthea (SA), apple (TTAp), Arizona 

 cypress (TTC), juniper (TTJ), cut-leaf or soft maple (TTM), 

 yellow pines (TTP), cherry (WCh), peach (WPe), Arizona cypress 

 (XSC), ponderosa pine (XSP), and citrus (YCt). In contrast, the 

 Cottonwood (TTCw), the honey locust (TTL), and the Jeffrey pine 

 (XSJf) show less than 50 percent of the years with multiple growth 

 layers. 



